sshd_config(5) — Linux manual page

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SSHD_CONFIG(5)             File Formats Manual            SSHD_CONFIG(5)

NAME         top

       sshd_config — OpenSSH daemon configuration file

DESCRIPTION         top

       sshd(8) reads configuration data from /etc/ssh/sshd_config (or
       the file specified with -f on the command line).  The file
       contains keyword-argument pairs, one per line.  Unless noted
       otherwise, for each keyword, the first obtained value will be
       used.  Lines starting with ‘#’ and empty lines are interpreted as
       comments.  Arguments may optionally be enclosed in double quotes
       (") in order to represent arguments containing spaces.

       The possible keywords and their meanings are as follows (note
       that keywords are case-insensitive and arguments are case-
       sensitive):

       AcceptEnv
               Specifies what environment variables sent by the client
               will be copied into the session's environ(7).  See
               SendEnv and SetEnv in ssh_config(5) for how to configure
               the client.  The TERM environment variable is always
               accepted whenever the client requests a pseudo-terminal
               as it is required by the protocol.  Variables are
               specified by name, which may contain the wildcard
               characters ‘*’ and ‘?’.  Multiple environment variables
               may be separated by whitespace or spread across multiple
               AcceptEnv directives.  Be warned that some environment
               variables could be used to bypass restricted user
               environments.  For this reason, care should be taken in
               the use of this directive.  The default is not to accept
               any environment variables.

       AddressFamily
               Specifies which address family should be used by sshd(8).
               Valid arguments are any (the default), inet (use IPv4
               only), or inet6 (use IPv6 only).

       AllowAgentForwarding
               Specifies whether ssh-agent(1) forwarding is permitted.
               The default is yes.  Note that disabling agent forwarding
               does not improve security unless users are also denied
               shell access, as they can always install their own
               forwarders.

       AllowGroups
               This keyword can be followed by a list of group name
               patterns, separated by spaces.  If specified, login is
               allowed only for users whose primary group or
               supplementary group list matches one of the patterns.
               Only group names are valid; a numerical group ID is not
               recognized.  By default, login is allowed for all groups.
               The allow/deny groups directives are processed in the
               following order: DenyGroups, AllowGroups.

               See PATTERNS in ssh_config(5) for more information on
               patterns.  This keyword may appear multiple times in
               sshd_config with each instance appending to the list.

       AllowStreamLocalForwarding
               Specifies whether StreamLocal (Unix-domain socket)
               forwarding is permitted.  The available options are yes
               (the default) or all to allow StreamLocal forwarding, no
               to prevent all StreamLocal forwarding, local to allow
               local (from the perspective of ssh(1)) forwarding only or
               remote to allow remote forwarding only.  Note that
               disabling StreamLocal forwarding does not improve
               security unless users are also denied shell access, as
               they can always install their own forwarders.

       AllowTcpForwarding
               Specifies whether TCP forwarding is permitted.  The
               available options are yes (the default) or all to allow
               TCP forwarding, no to prevent all TCP forwarding, local
               to allow local (from the perspective of ssh(1))
               forwarding only or remote to allow remote forwarding
               only.  Note that disabling TCP forwarding does not
               improve security unless users are also denied shell
               access, as they can always install their own forwarders.

       AllowUsers
               This keyword can be followed by a list of user name
               patterns, separated by spaces.  If specified, login is
               allowed only for user names that match one of the
               patterns.  Only user names are valid; a numerical user ID
               is not recognized.  By default, login is allowed for all
               users.  If the pattern takes the form USER@HOST then USER
               and HOST are separately checked, restricting logins to
               particular users from particular hosts.  HOST criteria
               may additionally contain addresses to match in CIDR
               address/masklen format.  The allow/deny users directives
               are processed in the following order: DenyUsers,
               AllowUsers.

               See PATTERNS in ssh_config(5) for more information on
               patterns.  This keyword may appear multiple times in
               sshd_config with each instance appending to the list.

       AuthenticationMethods
               Specifies the authentication methods that must be
               successfully completed for a user to be granted access.
               This option must be followed by one or more lists of
               comma-separated authentication method names, or by the
               single string any to indicate the default behaviour of
               accepting any single authentication method.  If the
               default is overridden, then successful authentication
               requires completion of every method in at least one of
               these lists.

               For example, "publickey,password
               publickey,keyboard-interactive" would require the user to
               complete public key authentication, followed by either
               password or keyboard interactive authentication.  Only
               methods that are next in one or more lists are offered at
               each stage, so for this example it would not be possible
               to attempt password or keyboard-interactive
               authentication before public key.

               For keyboard interactive authentication it is also
               possible to restrict authentication to a specific device
               by appending a colon followed by the device identifier
               bsdauth or pam.  depending on the server configuration.
               For example, "keyboard-interactive:bsdauth" would
               restrict keyboard interactive authentication to the
               bsdauth device.

               If the publickey method is listed more than once, sshd(8)
               verifies that keys that have been used successfully are
               not reused for subsequent authentications.  For example,
               "publickey,publickey" requires successful authentication
               using two different public keys.

               Note that each authentication method listed should also
               be explicitly enabled in the configuration.

               The available authentication methods are:
               "gssapi-with-mic", "hostbased", "keyboard-interactive",
               "none" (used for access to password-less accounts when
               PermitEmptyPasswords is enabled), "password" and
               "publickey".

       AuthorizedKeysCommand
               Specifies a program to be used to look up the user's
               public keys.  The program must be owned by root, not
               writable by group or others and specified by an absolute
               path.  Arguments to AuthorizedKeysCommand accept the
               tokens described in the “TOKENS” section.  If no
               arguments are specified then the username of the target
               user is used.

               The program should produce on standard output zero or
               more lines of authorized_keys output (see
               “AUTHORIZED_KEYS” in sshd(8)).  AuthorizedKeysCommand is
               tried after the usual AuthorizedKeysFile files and will
               not be executed if a matching key is found there.  By
               default, no AuthorizedKeysCommand is run.

       AuthorizedKeysCommandUser
               Specifies the user under whose account the
               AuthorizedKeysCommand is run.  It is recommended to use a
               dedicated user that has no other role on the host than
               running authorized keys commands.  If
               AuthorizedKeysCommand is specified but
               AuthorizedKeysCommandUser is not, then sshd(8) will
               refuse to start.

       AuthorizedKeysFile
               Specifies the file that contains the public keys used for
               user authentication.  The format is described in the
               AUTHORIZED_KEYS FILE FORMAT section of sshd(8).
               Arguments to AuthorizedKeysFile accept the tokens
               described in the “TOKENS” section.  After expansion,
               AuthorizedKeysFile is taken to be an absolute path or one
               relative to the user's home directory.  Multiple files
               may be listed, separated by whitespace.  Alternately this
               option may be set to none to skip checking for user keys
               in files.  The default is ".ssh/authorized_keys
               .ssh/authorized_keys2".

       AuthorizedPrincipalsCommand
               Specifies a program to be used to generate the list of
               allowed certificate principals as per
               AuthorizedPrincipalsFile.  The program must be owned by
               root, not writable by group or others and specified by an
               absolute path.  Arguments to AuthorizedPrincipalsCommand
               accept the tokens described in the “TOKENS” section.  If
               no arguments are specified then the username of the
               target user is used.

               The program should produce on standard output zero or
               more lines of AuthorizedPrincipalsFile output.  If either
               AuthorizedPrincipalsCommand or AuthorizedPrincipalsFile
               is specified, then certificates offered by the client for
               authentication must contain a principal that is listed.
               By default, no AuthorizedPrincipalsCommand is run.

       AuthorizedPrincipalsCommandUser
               Specifies the user under whose account the
               AuthorizedPrincipalsCommand is run.  It is recommended to
               use a dedicated user that has no other role on the host
               than running authorized principals commands.  If
               AuthorizedPrincipalsCommand is specified but
               AuthorizedPrincipalsCommandUser is not, then sshd(8) will
               refuse to start.

       AuthorizedPrincipalsFile
               Specifies a file that lists principal names that are
               accepted for certificate authentication.  When using
               certificates signed by a key listed in TrustedUserCAKeys,
               this file lists names, one of which must appear in the
               certificate for it to be accepted for authentication.
               Names are listed one per line preceded by key options (as
               described in “AUTHORIZED_KEYS FILE FORMAT” in sshd(8)).
               Empty lines and comments starting with ‘#’ are ignored.

               Arguments to AuthorizedPrincipalsFile accept the tokens
               described in the “TOKENS” section.  After expansion,
               AuthorizedPrincipalsFile is taken to be an absolute path
               or one relative to the user's home directory.  The
               default is none, i.e. not to use a principals file – in
               this case, the username of the user must appear in a
               certificate's principals list for it to be accepted.

               Note that AuthorizedPrincipalsFile is only used when
               authentication proceeds using a CA listed in
               TrustedUserCAKeys and is not consulted for certification
               authorities trusted via ~/.ssh/authorized_keys, though
               the principals= key option offers a similar facility (see
               sshd(8) for details).

       Banner  The contents of the specified file are sent to the remote
               user before authentication is allowed.  If the argument
               is none then no banner is displayed.  By default, no
               banner is displayed.

       CASignatureAlgorithms
               Specifies which algorithms are allowed for signing of
               certificates by certificate authorities (CAs).  The
               default is:

                     ssh-ed25519,ecdsa-sha2-nistp256,
                     ecdsa-sha2-nistp384,ecdsa-sha2-nistp521,
                     sk-ssh-ed25519@openssh.com,
                     sk-ecdsa-sha2-nistp256@openssh.com,
                     rsa-sha2-512,rsa-sha2-256

               If the specified list begins with a ‘+’ character, then
               the specified algorithms will be appended to the default
               set instead of replacing them.  If the specified list
               begins with a ‘-’ character, then the specified
               algorithms (including wildcards) will be removed from the
               default set instead of replacing them.

               Certificates signed using other algorithms will not be
               accepted for public key or host-based authentication.

       ChannelTimeout
               Specifies whether and how quickly sshd(8) should close
               inactive channels.  Timeouts are specified as one or more
               “type=interval” pairs separated by whitespace, where the
               “type” must be the special keyword “global” or a channel
               type name from the list below, optionally containing
               wildcard characters.

               The timeout value “interval” is specified in seconds or
               may use any of the units documented in the “TIME FORMATS”
               section.  For example, “session=5m” would cause
               interactive sessions to terminate after five minutes of
               inactivity.  Specifying a zero value disables the
               inactivity timeout.

               The special timeout “global” applies to all active
               channels, taken together.  Traffic on any active channel
               will reset the timeout, but when the timeout expires then
               all open channels will be closed.  Note that this global
               timeout is not matched by wildcards and must be specified
               explicitly.

               The available channel type names include:

               agent-connection
                       Open connections to ssh-agent(1).

               direct-tcpip, direct-streamlocal@openssh.com
                       Open TCP or Unix socket (respectively)
                       connections that have been established from a
                       ssh(1) local forwarding, i.e. LocalForward or
                       DynamicForward.

               forwarded-tcpip, forwarded-streamlocal@openssh.com
                       Open TCP or Unix socket (respectively)
                       connections that have been established to a
                       sshd(8) listening on behalf of a ssh(1) remote
                       forwarding, i.e. RemoteForward.

               session
                       The interactive main session, including shell
                       session, command execution, scp(1), sftp(1), etc.

               tun-connection
                       Open TunnelForward connections.

               x11-connection
                       Open X11 forwarding sessions.

               Note that in all the above cases, terminating an inactive
               session does not guarantee to remove all resources
               associated with the session, e.g. shell processes or X11
               clients relating to the session may continue to execute.

               Moreover, terminating an inactive channel or session does
               not necessarily close the SSH connection, nor does it
               prevent a client from requesting another channel of the
               same type.  In particular, expiring an inactive
               forwarding session does not prevent another identical
               forwarding from being subsequently created.

               The default is not to expire channels of any type for
               inactivity.

       ChrootDirectory
               Specifies the pathname of a directory to chroot(2) to
               after authentication.  At session startup sshd(8) checks
               that all components of the pathname are root-owned
               directories which are not writable by group or others.
               After the chroot, sshd(8) changes the working directory
               to the user's home directory.  Arguments to
               ChrootDirectory accept the tokens described in the
               “TOKENS” section.

               The ChrootDirectory must contain the necessary files and
               directories to support the user's session.  For an
               interactive session this requires at least a shell,
               typically sh(1), and basic /dev nodes such as null(4),
               zero(4), stdin(4), stdout(4), stderr(4), and tty(4)
               devices.  For file transfer sessions using SFTP no
               additional configuration of the environment is necessary
               if the in-process sftp-server is used, though sessions
               which use logging may require /dev/log inside the chroot
               directory on some operating systems (see sftp-server(8)
               for details).

               For safety, it is very important that the directory
               hierarchy be prevented from modification by other
               processes on the system (especially those outside the
               jail).  Misconfiguration can lead to unsafe environments
               which sshd(8) cannot detect.

               The default is none, indicating not to chroot(2).

       Ciphers
               Specifies the ciphers allowed.  Multiple ciphers must be
               comma-separated.  If the specified list begins with a ‘+’
               character, then the specified ciphers will be appended to
               the default set instead of replacing them.  If the
               specified list begins with a ‘-’ character, then the
               specified ciphers (including wildcards) will be removed
               from the default set instead of replacing them.  If the
               specified list begins with a ‘^’ character, then the
               specified ciphers will be placed at the head of the
               default set.

               The supported ciphers are:

                     3des-cbc
                     aes128-cbc
                     aes192-cbc
                     aes256-cbc
                     aes128-ctr
                     aes192-ctr
                     aes256-ctr
                     aes128-gcm@openssh.com
                     aes256-gcm@openssh.com
                     chacha20-poly1305@openssh.com

               The default is:

                     chacha20-poly1305@openssh.com,
                     aes128-ctr,aes192-ctr,aes256-ctr,
                     aes128-gcm@openssh.com,aes256-gcm@openssh.com

               The list of available ciphers may also be obtained using
               "ssh -Q cipher".

       ClientAliveCountMax
               Sets the number of client alive messages which may be
               sent without sshd(8) receiving any messages back from the
               client.  If this threshold is reached while client alive
               messages are being sent, sshd will disconnect the client,
               terminating the session.  It is important to note that
               the use of client alive messages is very different from
               TCPKeepAlive.  The client alive messages are sent through
               the encrypted channel and therefore will not be
               spoofable.  The TCP keepalive option enabled by
               TCPKeepAlive is spoofable.  The client alive mechanism is
               valuable when the client or server depend on knowing when
               a connection has become unresponsive.

               The default value is 3.  If ClientAliveInterval is set to
               15, and ClientAliveCountMax is left at the default,
               unresponsive SSH clients will be disconnected after
               approximately 45 seconds.  Setting a zero
               ClientAliveCountMax disables connection termination.

       ClientAliveInterval
               Sets a timeout interval in seconds after which if no data
               has been received from the client, sshd(8) will send a
               message through the encrypted channel to request a
               response from the client.  The default is 0, indicating
               that these messages will not be sent to the client.

       Compression
               Specifies whether compression is enabled after the user
               has authenticated successfully.  The argument must be
               yes, delayed (a legacy synonym for yes) or no.  The
               default is yes.

       DenyGroups
               This keyword can be followed by a list of group name
               patterns, separated by spaces.  Login is disallowed for
               users whose primary group or supplementary group list
               matches one of the patterns.  Only group names are valid;
               a numerical group ID is not recognized.  By default,
               login is allowed for all groups.  The allow/deny groups
               directives are processed in the following order:
               DenyGroups, AllowGroups.

               See PATTERNS in ssh_config(5) for more information on
               patterns.  This keyword may appear multiple times in
               sshd_config with each instance appending to the list.

       DenyUsers
               This keyword can be followed by a list of user name
               patterns, separated by spaces.  Login is disallowed for
               user names that match one of the patterns.  Only user
               names are valid; a numerical user ID is not recognized.
               By default, login is allowed for all users.  If the
               pattern takes the form USER@HOST then USER and HOST are
               separately checked, restricting logins to particular
               users from particular hosts.  HOST criteria may
               additionally contain addresses to match in CIDR
               address/masklen format.  The allow/deny users directives
               are processed in the following order: DenyUsers,
               AllowUsers.

               See PATTERNS in ssh_config(5) for more information on
               patterns.  This keyword may appear multiple times in
               sshd_config with each instance appending to the list.

       DisableForwarding
               Disables all forwarding features, including X11,
               ssh-agent(1), TCP and StreamLocal.  This option overrides
               all other forwarding-related options and may simplify
               restricted configurations.

       ExposeAuthInfo
               Writes a temporary file containing a list of
               authentication methods and public credentials (e.g. keys)
               used to authenticate the user.  The location of the file
               is exposed to the user session through the SSH_USER_AUTH
               environment variable.  The default is no.

       FingerprintHash
               Specifies the hash algorithm used when logging key
               fingerprints.  Valid options are: md5 and sha256.  The
               default is sha256.

       ForceCommand
               Forces the execution of the command specified by
               ForceCommand, ignoring any command supplied by the client
               and ~/.ssh/rc if present.  The command is invoked by
               using the user's login shell with the -c option.  This
               applies to shell, command, or subsystem execution.  It is
               most useful inside a Match block.  The command originally
               supplied by the client is available in the
               SSH_ORIGINAL_COMMAND environment variable.  Specifying a
               command of internal-sftp will force the use of an in-
               process SFTP server that requires no support files when
               used with ChrootDirectory.  The default is none.

       GatewayPorts
               Specifies whether remote hosts are allowed to connect to
               ports forwarded for the client.  By default, sshd(8)
               binds remote port forwardings to the loopback address.
               This prevents other remote hosts from connecting to
               forwarded ports.  GatewayPorts can be used to specify
               that sshd should allow remote port forwardings to bind to
               non-loopback addresses, thus allowing other hosts to
               connect.  The argument may be no to force remote port
               forwardings to be available to the local host only, yes
               to force remote port forwardings to bind to the wildcard
               address, or clientspecified to allow the client to select
               the address to which the forwarding is bound.  The
               default is no.

       GSSAPIAuthentication
               Specifies whether user authentication based on GSSAPI is
               allowed.  The default is no.

       GSSAPICleanupCredentials
               Specifies whether to automatically destroy the user's
               credentials cache on logout.  The default is yes.

       GSSAPIStrictAcceptorCheck
               Determines whether to be strict about the identity of the
               GSSAPI acceptor a client authenticates against.  If set
               to yes then the client must authenticate against the host
               service on the current hostname.  If set to no then the
               client may authenticate against any service key stored in
               the machine's default store.  This facility is provided
               to assist with operation on multi homed machines.  The
               default is yes.

       HostbasedAcceptedAlgorithms
               Specifies the signature algorithms that will be accepted
               for hostbased authentication as a list of comma-separated
               patterns.  Alternately if the specified list begins with
               a ‘+’ character, then the specified signature algorithms
               will be appended to the default set instead of replacing
               them.  If the specified list begins with a ‘-’ character,
               then the specified signature algorithms (including
               wildcards) will be removed from the default set instead
               of replacing them.  If the specified list begins with a
               ‘^’ character, then the specified signature algorithms
               will be placed at the head of the default set.  The
               default for this option is:

                  ssh-ed25519-cert-v01@openssh.com,
                  ecdsa-sha2-nistp256-cert-v01@openssh.com,
                  ecdsa-sha2-nistp384-cert-v01@openssh.com,
                  ecdsa-sha2-nistp521-cert-v01@openssh.com,
                  sk-ssh-ed25519-cert-v01@openssh.com,
                  sk-ecdsa-sha2-nistp256-cert-v01@openssh.com,
                  rsa-sha2-512-cert-v01@openssh.com,
                  rsa-sha2-256-cert-v01@openssh.com,
                  ssh-ed25519,
                  ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521,
                  sk-ssh-ed25519@openssh.com,
                  sk-ecdsa-sha2-nistp256@openssh.com,
                  rsa-sha2-512,rsa-sha2-256

               The list of available signature algorithms may also be
               obtained using "ssh -Q HostbasedAcceptedAlgorithms".
               This was formerly named HostbasedAcceptedKeyTypes.

       HostbasedAuthentication
               Specifies whether rhosts or /etc/hosts.equiv
               authentication together with successful public key client
               host authentication is allowed (host-based
               authentication).  The default is no.

       HostbasedUsesNameFromPacketOnly
               Specifies whether or not the server will attempt to
               perform a reverse name lookup when matching the name in
               the ~/.shosts, ~/.rhosts, and /etc/hosts.equiv files
               during HostbasedAuthentication.  A setting of yes means
               that sshd(8) uses the name supplied by the client rather
               than attempting to resolve the name from the TCP
               connection itself.  The default is no.

       HostCertificate
               Specifies a file containing a public host certificate.
               The certificate's public key must match a private host
               key already specified by HostKey.  The default behaviour
               of sshd(8) is not to load any certificates.

       HostKey
               Specifies a file containing a private host key used by
               SSH.  The defaults are /etc/ssh/ssh_host_ecdsa_key,
               /etc/ssh/ssh_host_ed25519_key and
               /etc/ssh/ssh_host_rsa_key.

               Note that sshd(8) will refuse to use a file if it is
               group/world-accessible and that the HostKeyAlgorithms
               option restricts which of the keys are actually used by
               sshd(8).

               It is possible to have multiple host key files.  It is
               also possible to specify public host key files instead.
               In this case operations on the private key will be
               delegated to an ssh-agent(1).

       HostKeyAgent
               Identifies the UNIX-domain socket used to communicate
               with an agent that has access to the private host keys.
               If the string "SSH_AUTH_SOCK" is specified, the location
               of the socket will be read from the SSH_AUTH_SOCK
               environment variable.

       HostKeyAlgorithms
               Specifies the host key signature algorithms that the
               server offers.  The default for this option is:

                  ssh-ed25519-cert-v01@openssh.com,
                  ecdsa-sha2-nistp256-cert-v01@openssh.com,
                  ecdsa-sha2-nistp384-cert-v01@openssh.com,
                  ecdsa-sha2-nistp521-cert-v01@openssh.com,
                  sk-ssh-ed25519-cert-v01@openssh.com,
                  sk-ecdsa-sha2-nistp256-cert-v01@openssh.com,
                  rsa-sha2-512-cert-v01@openssh.com,
                  rsa-sha2-256-cert-v01@openssh.com,
                  ssh-ed25519,
                  ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521,
                  sk-ssh-ed25519@openssh.com,
                  sk-ecdsa-sha2-nistp256@openssh.com,
                  rsa-sha2-512,rsa-sha2-256

               The list of available signature algorithms may also be
               obtained using "ssh -Q HostKeyAlgorithms".

       IgnoreRhosts
               Specifies whether to ignore per-user .rhosts and .shosts
               files during HostbasedAuthentication.  The system-wide
               /etc/hosts.equiv and /etc/shosts.equiv are still used
               regardless of this setting.

               Accepted values are yes (the default) to ignore all per-
               user files, shosts-only to allow the use of .shosts but
               to ignore .rhosts or no to allow both .shosts and rhosts.

       IgnoreUserKnownHosts
               Specifies whether sshd(8) should ignore the user's
               ~/.ssh/known_hosts during HostbasedAuthentication and use
               only the system-wide known hosts file
               /etc/ssh/ssh_known_hosts.  The default is “no”.

       Include
               Include the specified configuration file(s).  Multiple
               pathnames may be specified and each pathname may contain
               glob(7) wildcards that will be expanded and processed in
               lexical order.  Files without absolute paths are assumed
               to be in /etc/ssh.  An Include directive may appear
               inside a Match block to perform conditional inclusion.

       IPQoS   Specifies the IPv4 type-of-service or DSCP class for the
               connection.  Accepted values are af11, af12, af13, af21,
               af22, af23, af31, af32, af33, af41, af42, af43, cs0, cs1,
               cs2, cs3, cs4, cs5, cs6, cs7, ef, le, lowdelay,
               throughput, reliability, a numeric value, or none to use
               the operating system default.  This option may take one
               or two arguments, separated by whitespace.  If one
               argument is specified, it is used as the packet class
               unconditionally.  If two values are specified, the first
               is automatically selected for interactive sessions and
               the second for non-interactive sessions.  The default is
               af21 (Low-Latency Data) for interactive sessions and cs1
               (Lower Effort) for non-interactive sessions.

       KbdInteractiveAuthentication
               Specifies whether to allow keyboard-interactive
               authentication.  All authentication styles from
               login.conf(5) are supported.  The default is yes.  The
               argument to this keyword must be yes or no.
               ChallengeResponseAuthentication is a deprecated alias for
               this.

       KerberosAuthentication
               Specifies whether the password provided by the user for
               PasswordAuthentication will be validated through the
               Kerberos KDC.  To use this option, the server needs a
               Kerberos servtab which allows the verification of the
               KDC's identity.  The default is no.

       KerberosGetAFSToken
               If AFS is active and the user has a Kerberos 5 TGT,
               attempt to acquire an AFS token before accessing the
               user's home directory.  The default is no.

       KerberosOrLocalPasswd
               If password authentication through Kerberos fails then
               the password will be validated via any additional local
               mechanism such as /etc/passwd.  The default is yes.

       KerberosTicketCleanup
               Specifies whether to automatically destroy the user's
               ticket cache file on logout.  The default is yes.

       KexAlgorithms
               Specifies the available KEX (Key Exchange) algorithms.
               Multiple algorithms must be comma-separated.  Alternately
               if the specified list begins with a ‘+’ character, then
               the specified algorithms will be appended to the default
               set instead of replacing them.  If the specified list
               begins with a ‘-’ character, then the specified
               algorithms (including wildcards) will be removed from the
               default set instead of replacing them.  If the specified
               list begins with a ‘^’ character, then the specified
               algorithms will be placed at the head of the default set.
               The supported algorithms are:

                     curve25519-sha256
                     curve25519-sha256@libssh.org
                     diffie-hellman-group1-sha1
                     diffie-hellman-group14-sha1
                     diffie-hellman-group14-sha256
                     diffie-hellman-group16-sha512
                     diffie-hellman-group18-sha512
                     diffie-hellman-group-exchange-sha1
                     diffie-hellman-group-exchange-sha256
                     ecdh-sha2-nistp256
                     ecdh-sha2-nistp384
                     ecdh-sha2-nistp521
                     sntrup761x25519-sha512@openssh.com

               The default is:

                     sntrup761x25519-sha512@openssh.com,
                     curve25519-sha256,curve25519-sha256@libssh.org,
                     ecdh-sha2-nistp256,ecdh-sha2-nistp384,ecdh-sha2-nistp521,
                     diffie-hellman-group-exchange-sha256,
                     diffie-hellman-group16-sha512,diffie-hellman-group18-sha512,
                     diffie-hellman-group14-sha256

               The list of available key exchange algorithms may also be
               obtained using "ssh -Q KexAlgorithms".

       ListenAddress
               Specifies the local addresses sshd(8) should listen on.
               The following forms may be used:

                     ListenAddress hostname|address [rdomain domain]
                     ListenAddress hostname:port [rdomain domain]
                     ListenAddress IPv4_address:port [rdomain domain]
                     ListenAddress [hostname|address]:port [rdomain
                     domain]

               The optional rdomain qualifier requests sshd(8) listen in
               an explicit routing domain.  If port is not specified,
               sshd will listen on the address and all Port options
               specified.  The default is to listen on all local
               addresses on the current default routing domain.
               Multiple ListenAddress options are permitted.  For more
               information on routing domains, see rdomain(4).

       LoginGraceTime
               The server disconnects after this time if the user has
               not successfully logged in.  If the value is 0, there is
               no time limit.  The default is 120 seconds.

       LogLevel
               Gives the verbosity level that is used when logging
               messages from sshd(8).  The possible values are: QUIET,
               FATAL, ERROR, INFO, VERBOSE, DEBUG, DEBUG1, DEBUG2, and
               DEBUG3.  The default is INFO.  DEBUG and DEBUG1 are
               equivalent.  DEBUG2 and DEBUG3 each specify higher levels
               of debugging output.  Logging with a DEBUG level violates
               the privacy of users and is not recommended.

       LogVerbose
               Specify one or more overrides to LogLevel.  An override
               consists of a pattern lists that matches the source file,
               function and line number to force detailed logging for.
               For example, an override pattern of:

                     kex.c:*:1000,*:kex_exchange_identification():*,packet.c:*

               would enable detailed logging for line 1000 of kex.c,
               everything in the kex_exchange_identification() function,
               and all code in the packet.c file.  This option is
               intended for debugging and no overrides are enabled by
               default.

       MACs    Specifies the available MAC (message authentication code)
               algorithms.  The MAC algorithm is used for data integrity
               protection.  Multiple algorithms must be comma-separated.
               If the specified list begins with a ‘+’ character, then
               the specified algorithms will be appended to the default
               set instead of replacing them.  If the specified list
               begins with a ‘-’ character, then the specified
               algorithms (including wildcards) will be removed from the
               default set instead of replacing them.  If the specified
               list begins with a ‘^’ character, then the specified
               algorithms will be placed at the head of the default set.

               The algorithms that contain "-etm" calculate the MAC
               after encryption (encrypt-then-mac).  These are
               considered safer and their use recommended.  The
               supported MACs are:

                     hmac-md5
                     hmac-md5-96
                     hmac-sha1
                     hmac-sha1-96
                     hmac-sha2-256
                     hmac-sha2-512
                     umac-64@openssh.com
                     umac-128@openssh.com
                     hmac-md5-etm@openssh.com
                     hmac-md5-96-etm@openssh.com
                     hmac-sha1-etm@openssh.com
                     hmac-sha1-96-etm@openssh.com
                     hmac-sha2-256-etm@openssh.com
                     hmac-sha2-512-etm@openssh.com
                     umac-64-etm@openssh.com
                     umac-128-etm@openssh.com

               The default is:

                     umac-64-etm@openssh.com,umac-128-etm@openssh.com,
                     hmac-sha2-256-etm@openssh.com,hmac-sha2-512-etm@openssh.com,
                     hmac-sha1-etm@openssh.com,
                     umac-64@openssh.com,umac-128@openssh.com,
                     hmac-sha2-256,hmac-sha2-512,hmac-sha1

               The list of available MAC algorithms may also be obtained
               using "ssh -Q mac".

       Match   Introduces a conditional block.  If all of the criteria
               on the Match line are satisfied, the keywords on the
               following lines override those set in the global section
               of the config file, until either another Match line or
               the end of the file.  If a keyword appears in multiple
               Match blocks that are satisfied, only the first instance
               of the keyword is applied.

               The arguments to Match are one or more criteria-pattern
               pairs or the single token All which matches all criteria.
               The available criteria are User, Group, Host,
               LocalAddress, LocalPort, RDomain, and Address (with
               RDomain representing the rdomain(4) on which the
               connection was received).

               The match patterns may consist of single entries or
               comma-separated lists and may use the wildcard and
               negation operators described in the “PATTERNS” section of
               ssh_config(5).

               The patterns in an Address criteria may additionally
               contain addresses to match in CIDR address/masklen
               format, such as 192.0.2.0/24 or 2001:db8::/32.  Note that
               the mask length provided must be consistent with the
               address - it is an error to specify a mask length that is
               too long for the address or one with bits set in this
               host portion of the address.  For example, 192.0.2.0/33
               and 192.0.2.0/8, respectively.

               Only a subset of keywords may be used on the lines
               following a Match keyword.  Available keywords are
               AcceptEnv, AllowAgentForwarding, AllowGroups,
               AllowStreamLocalForwarding, AllowTcpForwarding,
               AllowUsers, AuthenticationMethods, AuthorizedKeysCommand,
               AuthorizedKeysCommandUser, AuthorizedKeysFile,
               AuthorizedPrincipalsCommand,
               AuthorizedPrincipalsCommandUser,
               AuthorizedPrincipalsFile, Banner, CASignatureAlgorithms,
               ChannelTimeout, ChrootDirectory, ClientAliveCountMax,
               ClientAliveInterval, DenyGroups, DenyUsers,
               DisableForwarding, ExposeAuthInfo, ForceCommand,
               GatewayPorts, GSSAPIAuthentication,
               HostbasedAcceptedAlgorithms, HostbasedAuthentication,
               HostbasedUsesNameFromPacketOnly, IgnoreRhosts, Include,
               IPQoS, KbdInteractiveAuthentication,
               KerberosAuthentication, LogLevel, MaxAuthTries,
               MaxSessions, PasswordAuthentication,
               PermitEmptyPasswords, PermitListen, PermitOpen,
               PermitRootLogin, PermitTTY, PermitTunnel, PermitUserRC,
               PubkeyAcceptedAlgorithms, PubkeyAuthentication,
               PubkeyAuthOptions, RekeyLimit, RevokedKeys, RDomain,
               SetEnv, StreamLocalBindMask, StreamLocalBindUnlink,
               TrustedUserCAKeys, UnusedConnectionTimeout,
               X11DisplayOffset, X11Forwarding and X11UseLocalhost.

       MaxAuthTries
               Specifies the maximum number of authentication attempts
               permitted per connection.  Once the number of failures
               reaches half this value, additional failures are logged.
               The default is 6.

       MaxSessions
               Specifies the maximum number of open shell, login or
               subsystem (e.g. sftp) sessions permitted per network
               connection.  Multiple sessions may be established by
               clients that support connection multiplexing.  Setting
               MaxSessions to 1 will effectively disable session
               multiplexing, whereas setting it to 0 will prevent all
               shell, login and subsystem sessions while still
               permitting forwarding.  The default is 10.

       MaxStartups
               Specifies the maximum number of concurrent
               unauthenticated connections to the SSH daemon.
               Additional connections will be dropped until
               authentication succeeds or the LoginGraceTime expires for
               a connection.  The default is 10:30:100.

               Alternatively, random early drop can be enabled by
               specifying the three colon separated values
               start:rate:full (e.g. "10:30:60").  sshd(8) will refuse
               connection attempts with a probability of rate/100 (30%)
               if there are currently start (10) unauthenticated
               connections.  The probability increases linearly and all
               connection attempts are refused if the number of
               unauthenticated connections reaches full (60).

       ModuliFile
               Specifies the moduli(5) file that contains the Diffie-
               Hellman groups used for the
               “diffie-hellman-group-exchange-sha1” and
               “diffie-hellman-group-exchange-sha256” key exchange
               methods.  The default is /etc/moduli.

       PasswordAuthentication
               Specifies whether password authentication is allowed.
               The default is yes.

       PermitEmptyPasswords
               When password authentication is allowed, it specifies
               whether the server allows login to accounts with empty
               password strings.  The default is no.

       PermitListen
               Specifies the addresses/ports on which a remote TCP port
               forwarding may listen.  The listen specification must be
               one of the following forms:

                     PermitListen port
                     PermitListen host:port

               Multiple permissions may be specified by separating them
               with whitespace.  An argument of any can be used to
               remove all restrictions and permit any listen requests.
               An argument of none can be used to prohibit all listen
               requests.  The host name may contain wildcards as
               described in the PATTERNS section in ssh_config(5).  The
               wildcard ‘*’ can also be used in place of a port number
               to allow all ports.  By default all port forwarding
               listen requests are permitted.  Note that the
               GatewayPorts option may further restrict which addresses
               may be listened on.  Note also that ssh(1) will request a
               listen host of “localhost” if no listen host was
               specifically requested, and this name is treated
               differently to explicit localhost addresses of
               “127.0.0.1” and “::1”.

       PermitOpen
               Specifies the destinations to which TCP port forwarding
               is permitted.  The forwarding specification must be one
               of the following forms:

                     PermitOpen host:port
                     PermitOpen IPv4_addr:port
                     PermitOpen [IPv6_addr]:port

               Multiple forwards may be specified by separating them
               with whitespace.  An argument of any can be used to
               remove all restrictions and permit any forwarding
               requests.  An argument of none can be used to prohibit
               all forwarding requests.  The wildcard ‘*’ can be used
               for host or port to allow all hosts or ports
               respectively.  Otherwise, no pattern matching or address
               lookups are performed on supplied names.  By default all
               port forwarding requests are permitted.

       PermitRootLogin
               Specifies whether root can log in using ssh(1).  The
               argument must be yes, prohibit-password,
               forced-commands-only, or no.  The default is
               prohibit-password.

               If this option is set to prohibit-password (or its
               deprecated alias, without-password), password and
               keyboard-interactive authentication are disabled for
               root.

               If this option is set to forced-commands-only, root login
               with public key authentication will be allowed, but only
               if the command option has been specified (which may be
               useful for taking remote backups even if root login is
               normally not allowed).  All other authentication methods
               are disabled for root.

               If this option is set to no, root is not allowed to log
               in.

       PermitTTY
               Specifies whether pty(4) allocation is permitted.  The
               default is yes.

       PermitTunnel
               Specifies whether tun(4) device forwarding is allowed.
               The argument must be yes, point-to-point (layer 3),
               ethernet (layer 2), or no.  Specifying yes permits both
               point-to-point and ethernet.  The default is no.

               Independent of this setting, the permissions of the
               selected tun(4) device must allow access to the user.

       PermitUserEnvironment
               Specifies whether ~/.ssh/environment and environment=
               options in ~/.ssh/authorized_keys are processed by
               sshd(8).  Valid options are yes, no or a pattern-list
               specifying which environment variable names to accept
               (for example "LANG,LC_*").  The default is no.  Enabling
               environment processing may enable users to bypass access
               restrictions in some configurations using mechanisms such
               as LD_PRELOAD.

       PermitUserRC
               Specifies whether any ~/.ssh/rc file is executed.  The
               default is yes.

       PerSourceMaxStartups
               Specifies the number of unauthenticated connections
               allowed from a given source address, or “none” if there
               is no limit.  This limit is applied in addition to
               MaxStartups, whichever is lower.  The default is none.

       PerSourceNetBlockSize
               Specifies the number of bits of source address that are
               grouped together for the purposes of applying
               PerSourceMaxStartups limits.  Values for IPv4 and
               optionally IPv6 may be specified, separated by a colon.
               The default is 32:128, which means each address is
               considered individually.

       PidFile
               Specifies the file that contains the process ID of the
               SSH daemon, or none to not write one.  The default is
               /var/run/sshd.pid.

       Port    Specifies the port number that sshd(8) listens on.  The
               default is 22.  Multiple options of this type are
               permitted.  See also ListenAddress.

       PrintLastLog
               Specifies whether sshd(8) should print the date and time
               of the last user login when a user logs in interactively.
               The default is yes.

       PrintMotd
               Specifies whether sshd(8) should print /etc/motd when a
               user logs in interactively.  (On some systems it is also
               printed by the shell, /etc/profile, or equivalent.)  The
               default is yes.

       PubkeyAcceptedAlgorithms
               Specifies the signature algorithms that will be accepted
               for public key authentication as a list of comma-
               separated patterns.  Alternately if the specified list
               begins with a ‘+’ character, then the specified
               algorithms will be appended to the default set instead of
               replacing them.  If the specified list begins with a ‘-’
               character, then the specified algorithms (including
               wildcards) will be removed from the default set instead
               of replacing them.  If the specified list begins with a
               ‘^’ character, then the specified algorithms will be
               placed at the head of the default set.  The default for
               this option is:

                  ssh-ed25519-cert-v01@openssh.com,
                  ecdsa-sha2-nistp256-cert-v01@openssh.com,
                  ecdsa-sha2-nistp384-cert-v01@openssh.com,
                  ecdsa-sha2-nistp521-cert-v01@openssh.com,
                  sk-ssh-ed25519-cert-v01@openssh.com,
                  sk-ecdsa-sha2-nistp256-cert-v01@openssh.com,
                  rsa-sha2-512-cert-v01@openssh.com,
                  rsa-sha2-256-cert-v01@openssh.com,
                  ssh-ed25519,
                  ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521,
                  sk-ssh-ed25519@openssh.com,
                  sk-ecdsa-sha2-nistp256@openssh.com,
                  rsa-sha2-512,rsa-sha2-256

               The list of available signature algorithms may also be
               obtained using "ssh -Q PubkeyAcceptedAlgorithms".

       PubkeyAuthOptions
               Sets one or more public key authentication options.  The
               supported keywords are: none (the default; indicating no
               additional options are enabled), touch-required and
               verify-required.

               The touch-required option causes public key
               authentication using a FIDO authenticator algorithm (i.e.
               ecdsa-sk or ed25519-sk) to always require the signature
               to attest that a physically present user explicitly
               confirmed the authentication (usually by touching the
               authenticator).  By default, sshd(8) requires user
               presence unless overridden with an authorized_keys
               option.  The touch-required flag disables this override.

               The verify-required option requires a FIDO key signature
               attest that the user was verified, e.g. via a PIN.

               Neither the touch-required or verify-required options
               have any effect for other, non-FIDO, public key types.

       PubkeyAuthentication
               Specifies whether public key authentication is allowed.
               The default is yes.

       RekeyLimit
               Specifies the maximum amount of data that may be
               transmitted or received before the session key is
               renegotiated, optionally followed by a maximum amount of
               time that may pass before the session key is
               renegotiated.  The first argument is specified in bytes
               and may have a suffix of ‘K’, ‘M’, or ‘G’ to indicate
               Kilobytes, Megabytes, or Gigabytes, respectively.  The
               default is between ‘1G’ and ‘4G’, depending on the
               cipher.  The optional second value is specified in
               seconds and may use any of the units documented in the
               “TIME FORMATS” section.  The default value for RekeyLimit
               is default none, which means that rekeying is performed
               after the cipher's default amount of data has been sent
               or received and no time based rekeying is done.

       RequiredRSASize
               Specifies the minimum RSA key size (in bits) that sshd(8)
               will accept.  User and host-based authentication keys
               smaller than this limit will be refused.  The default is
               1024 bits.  Note that this limit may only be raised from
               the default.

       RevokedKeys
               Specifies revoked public keys file, or none to not use
               one.  Keys listed in this file will be refused for public
               key authentication.  Note that if this file is not
               readable, then public key authentication will be refused
               for all users.  Keys may be specified as a text file,
               listing one public key per line, or as an OpenSSH Key
               Revocation List (KRL) as generated by ssh-keygen(1).  For
               more information on KRLs, see the KEY REVOCATION LISTS
               section in ssh-keygen(1).

       RDomain
               Specifies an explicit routing domain that is applied
               after authentication has completed.  The user session, as
               well as any forwarded or listening IP sockets, will be
               bound to this rdomain(4).  If the routing domain is set
               to %D, then the domain in which the incoming connection
               was received will be applied.

       SecurityKeyProvider
               Specifies a path to a library that will be used when
               loading FIDO authenticator-hosted keys, overriding the
               default of using the built-in USB HID support.

       SetEnv  Specifies one or more environment variables to set in
               child sessions started by sshd(8) as “NAME=VALUE”.  The
               environment value may be quoted (e.g. if it contains
               whitespace characters).  Environment variables set by
               SetEnv override the default environment and any variables
               specified by the user via AcceptEnv or
               PermitUserEnvironment.

       StreamLocalBindMask
               Sets the octal file creation mode mask (umask) used when
               creating a Unix-domain socket file for local or remote
               port forwarding.  This option is only used for port
               forwarding to a Unix-domain socket file.

               The default value is 0177, which creates a Unix-domain
               socket file that is readable and writable only by the
               owner.  Note that not all operating systems honor the
               file mode on Unix-domain socket files.

       StreamLocalBindUnlink
               Specifies whether to remove an existing Unix-domain
               socket file for local or remote port forwarding before
               creating a new one.  If the socket file already exists
               and StreamLocalBindUnlink is not enabled, sshd will be
               unable to forward the port to the Unix-domain socket
               file.  This option is only used for port forwarding to a
               Unix-domain socket file.

               The argument must be yes or no.  The default is no.

       StrictModes
               Specifies whether sshd(8) should check file modes and
               ownership of the user's files and home directory before
               accepting login.  This is normally desirable because
               novices sometimes accidentally leave their directory or
               files world-writable.  The default is yes.  Note that
               this does not apply to ChrootDirectory, whose permissions
               and ownership are checked unconditionally.

       Subsystem
               Configures an external subsystem (e.g. file transfer
               daemon).  Arguments should be a subsystem name and a
               command (with optional arguments) to execute upon
               subsystem request.

               The command sftp-server implements the SFTP file transfer
               subsystem.

               Alternately the name internal-sftp implements an in-
               process SFTP server.  This may simplify configurations
               using ChrootDirectory to force a different filesystem
               root on clients.  It accepts the same command line
               arguments as sftp-server and even though it is in-
               process, settings such as LogLevel or SyslogFacility do
               not apply to it and must be set explicitly via command
               line arguments.

               By default no subsystems are defined.

       SyslogFacility
               Gives the facility code that is used when logging
               messages from sshd(8).  The possible values are: DAEMON,
               USER, AUTH, LOCAL0, LOCAL1, LOCAL2, LOCAL3, LOCAL4,
               LOCAL5, LOCAL6, LOCAL7.  The default is AUTH.

       TCPKeepAlive
               Specifies whether the system should send TCP keepalive
               messages to the other side.  If they are sent, death of
               the connection or crash of one of the machines will be
               properly noticed.  However, this means that connections
               will die if the route is down temporarily, and some
               people find it annoying.  On the other hand, if TCP
               keepalives are not sent, sessions may hang indefinitely
               on the server, leaving "ghost" users and consuming server
               resources.

               The default is yes (to send TCP keepalive messages), and
               the server will notice if the network goes down or the
               client host crashes.  This avoids infinitely hanging
               sessions.

               To disable TCP keepalive messages, the value should be
               set to no.

       TrustedUserCAKeys
               Specifies a file containing public keys of certificate
               authorities that are trusted to sign user certificates
               for authentication, or none to not use one.  Keys are
               listed one per line; empty lines and comments starting
               with ‘#’ are allowed.  If a certificate is presented for
               authentication and has its signing CA key listed in this
               file, then it may be used for authentication for any user
               listed in the certificate's principals list.  Note that
               certificates that lack a list of principals will not be
               permitted for authentication using TrustedUserCAKeys.
               For more details on certificates, see the CERTIFICATES
               section in ssh-keygen(1).

       UnusedConnectionTimeout
               Specifies whether and how quickly sshd(8) should close
               client connections with no open channels.  Open channels
               include active shell, command execution or subsystem
               sessions, connected network, socket, agent or X11
               forwardings.  Forwarding listeners, such as those from
               the ssh(1) -R flag, are not considered as open channels
               and do not prevent the timeout.  The timeout value is
               specified in seconds or may use any of the units
               documented in the “TIME FORMATS” section.

               Note that this timeout starts when the client connection
               completes user authentication but before the client has
               an opportunity to open any channels.  Caution should be
               used when using short timeout values, as they may not
               provide sufficient time for the client to request and
               open its channels before terminating the connection.

               The default none is to never expire connections for
               having no open channels.  This option may be useful in
               conjunction with ChannelTimeout.

       UseDNS  Specifies whether sshd(8) should look up the remote host
               name, and to check that the resolved host name for the
               remote IP address maps back to the very same IP address.

               If this option is set to no (the default) then only
               addresses and not host names may be used in
               ~/.ssh/authorized_keys from and sshd_config Match Host
               directives.

       UsePAM  Enables the Pluggable Authentication Module interface.
               If set to yes this will enable PAM authentication using
               KbdInteractiveAuthentication and PasswordAuthentication
               in addition to PAM account and session module processing
               for all authentication types.

               Because PAM keyboard-interactive authentication usually
               serves an equivalent role to password authentication, you
               should disable either PasswordAuthentication or
               KbdInteractiveAuthentication.

               If UsePAM is enabled, you will not be able to run sshd(8)
               as a non-root user.  The default is no.

       VersionAddendum
               Optionally specifies additional text to append to the SSH
               protocol banner sent by the server upon connection.  The
               default is none.

       X11DisplayOffset
               Specifies the first display number available for
               sshd(8)'s X11 forwarding.  This prevents sshd from
               interfering with real X11 servers.  The default is 10.

       X11Forwarding
               Specifies whether X11 forwarding is permitted.  The
               argument must be yes or no.  The default is no.

               When X11 forwarding is enabled, there may be additional
               exposure to the server and to client displays if the
               sshd(8) proxy display is configured to listen on the
               wildcard address (see X11UseLocalhost), though this is
               not the default.  Additionally, the authentication
               spoofing and authentication data verification and
               substitution occur on the client side.  The security risk
               of using X11 forwarding is that the client's X11 display
               server may be exposed to attack when the SSH client
               requests forwarding (see the warnings for ForwardX11 in
               ssh_config(5)).  A system administrator may have a stance
               in which they want to protect clients that may expose
               themselves to attack by unwittingly requesting X11
               forwarding, which can warrant a no setting.

               Note that disabling X11 forwarding does not prevent users
               from forwarding X11 traffic, as users can always install
               their own forwarders.

       X11UseLocalhost
               Specifies whether sshd(8) should bind the X11 forwarding
               server to the loopback address or to the wildcard
               address.  By default, sshd binds the forwarding server to
               the loopback address and sets the hostname part of the
               DISPLAY environment variable to localhost.  This prevents
               remote hosts from connecting to the proxy display.
               However, some older X11 clients may not function with
               this configuration.  X11UseLocalhost may be set to no to
               specify that the forwarding server should be bound to the
               wildcard address.  The argument must be yes or no.  The
               default is yes.

       XAuthLocation
               Specifies the full pathname of the xauth(1) program, or
               none to not use one.  The default is
               /usr/X11R6/bin/xauth.

TIME FORMATS         top

       sshd(8) command-line arguments and configuration file options
       that specify time may be expressed using a sequence of the form:
       time[qualifier], where time is a positive integer value and
       qualifier is one of the following:

             ⟨none⟩  seconds
             s | S   seconds
             m | M   minutes
             h | H   hours
             d | D   days
             w | W   weeks

       Each member of the sequence is added together to calculate the
       total time value.

       Time format examples:

             600     600 seconds (10 minutes)
             10m     10 minutes
             1h30m   1 hour 30 minutes (90 minutes)

TOKENS         top

       Arguments to some keywords can make use of tokens, which are
       expanded at runtime:

             %%    A literal ‘%’.
             %C    Identifies the connection endpoints, containing four
                   space-separated values: client address, client port
                   number, server address, and server port number.
             %D    The routing domain in which the incoming connection
                   was received.
             %F    The fingerprint of the CA key.
             %f    The fingerprint of the key or certificate.
             %h    The home directory of the user.
             %i    The key ID in the certificate.
             %K    The base64-encoded CA key.
             %k    The base64-encoded key or certificate for
                   authentication.
             %s    The serial number of the certificate.
             %T    The type of the CA key.
             %t    The key or certificate type.
             %U    The numeric user ID of the target user.
             %u    The username.

       AuthorizedKeysCommand accepts the tokens %%, %C, %D, %f, %h, %k,
       %t, %U, and %u.

       AuthorizedKeysFile accepts the tokens %%, %h, %U, and %u.

       AuthorizedPrincipalsCommand accepts the tokens %%, %C, %D, %F,
       %f, %h, %i, %K, %k, %s, %T, %t, %U, and %u.

       AuthorizedPrincipalsFile accepts the tokens %%, %h, %U, and %u.

       ChrootDirectory accepts the tokens %%, %h, %U, and %u.

       RoutingDomain accepts the token %D.

FILES         top

       /etc/ssh/sshd_config
               Contains configuration data for sshd(8).  This file
               should be writable by root only, but it is recommended
               (though not necessary) that it be world-readable.

SEE ALSO         top

       sftp-server(8), sshd(8)

AUTHORS         top

       OpenSSH is a derivative of the original and free ssh 1.2.12
       release by Tatu Ylonen.  Aaron Campbell, Bob Beck, Markus Friedl,
       Niels Provos, Theo de Raadt and Dug Song removed many bugs, re-
       added newer features and created OpenSSH.  Markus Friedl
       contributed the support for SSH protocol versions 1.5 and 2.0.
       Niels Provos and Markus Friedl contributed support for privilege
       separation.

COLOPHON         top

       This page is part of the openssh (Portable OpenSSH) project.
       Information about the project can be found at
       http://www.openssh.com/portable.html.  If you have a bug report
       for this manual page, see ⟨http://www.openssh.com/report.html⟩.
       This page was obtained from the tarball openssh-9.7p1.tar.gz
       fetched from
       ⟨http://ftp.eu.openbsd.org/pub/OpenBSD/OpenSSH/portable/⟩ on
       2024-06-14.  If you discover any rendering problems in this HTML
       version of the page, or you believe there is a better or more up-
       to-date source for the page, or you have corrections or
       improvements to the information in this COLOPHON (which is not
       part of the original manual page), send a mail to
       man-pages@man7.org

GNU                         February 21, 2024             SSHD_CONFIG(5)

Pages that refer to this page: userdbctl(1)