ssh-add(1) — Linux manual page


SSH-ADD(1)               General Commands Manual              SSH-ADD(1)

NAME         top

       ssh-add — adds private key identities to the OpenSSH
       authentication agent

SYNOPSIS         top

       ssh-add [-cCDdKkLlqvXx] [-E fingerprint_hash] [-H hostkey_file]
       [-h destination_constraint] [-S provider] [-t life] [file ...]
       ssh-add -s pkcs11 [-vC] [certificate ...] ssh-add -e pkcs11
       ssh-add -T pubkey ...

DESCRIPTION         top

       adds private key identities to the authentication agent,
       ssh-agent(1).  When run without arguments, it adds the files
       ~/.ssh/id_rsa, ~/.ssh/id_ecdsa, ~/.ssh/id_ecdsa_sk,
       ~/.ssh/id_ed25519, ~/.ssh/id_ed25519_sk, and ~/.ssh/id_dsa.
       After loading a private key, will try to load corresponding
       certificate information from the filename obtained by appending to the name of the private key file.  Alternative file
       names can be given on the command line.

       If any file requires a passphrase, asks for the passphrase from
       the user.  The passphrase is read from the user's tty.  retries
       the last passphrase if multiple identity files are given.

       The authentication agent must be running and the SSH_AUTH_SOCK
       environment variable must contain the name of its socket for to

       The options are as follows:

       -c      Indicates that added identities should be subject to
               confirmation before being used for authentication.
               Confirmation is performed by ssh-askpass(1).  Successful
               confirmation is signaled by a zero exit status from
               ssh-askpass(1), rather than text entered into the

       -C      When loading keys into or deleting keys from the agent,
               process certificates only and skip plain keys.

       -D      Deletes all identities from the agent.

       -d      Instead of adding identities, removes identities from the
               agent.  If has been run without arguments, the keys for
               the default identities and their corresponding
               certificates will be removed.  Otherwise, the argument
               list will be interpreted as a list of paths to public key
               files to specify keys and certificates to be removed from
               the agent.  If no public key is found at a given path,
               will append .pub and retry.  If the argument list
               consists of “-” then will read public keys to be removed
               from standard input.

       -E fingerprint_hash
               Specifies the hash algorithm used when displaying key
               fingerprints.  Valid options are: “md5” and “sha256”.
               The default is “sha256”.

       -e pkcs11
               Remove keys provided by the PKCS#11 shared library

       -H hostkey_file
               Specifies a known hosts file to look up hostkeys when
               using destination-constrained keys via the -h flag.  This
               option may be specified multiple times to allow multiple
               files to be searched.  If no files are specified, will
               use the default ssh_config(5) known hosts files:
               ~/.ssh/known_hosts, ~/.ssh/known_hosts2,
               /etc/ssh/ssh_known_hosts, and /etc/ssh/ssh_known_hosts2.

       -h destination_constraint
               When adding keys, constrain them to be usable only
               through specific hosts or to specific destinations.

               Destination constraints of the form
               ‘[user@]dest-hostname’ permit use of the key only from
               the origin host (the one running ssh-agent(1)) to the
               listed destination host, with optional user name.

               Constraints of the form
               ‘src-hostname>[user@]dst-hostname’ allow a key available
               on a forwarded ssh-agent(1) to be used through a
               particular host (as specified by ‘src-hostname’) to
               authenticate to a further host, specified by

               Multiple destination constraints may be added when
               loading keys.  When attempting authentication with a key
               that has destination constraints, the whole connection
               path, including ssh-agent(1) forwarding, is tested
               against those constraints and each hop must be permitted
               for the attempt to succeed.  For example, if key is
               forwarded to a remote host, ‘host-b’, and is attempting
               authentication to another host, ‘host-c’, then the
               operation will be successful only if ‘host-b’ was
               permitted from the origin host and the subsequent
               ‘host-b>host-c’ hop is also permitted by destination

               Hosts are identified by their host keys, and are looked
               up from known hosts files by .  Wildcards patterns may be
               used for hostnames and certificate host keys are
               supported.  By default, keys added by are not destination

               Destination constraints were added in OpenSSH release
               8.9.  Support in both the remote SSH client and server is
               required when using destination-constrained keys over a
               forwarded ssh-agent(1) channel.

               It is also important to note that destination constraints
               can only be enforced by ssh-agent(1) when a key is used,
               or when it is forwarded by a cooperating ssh(1).
               Specifically, it does not prevent an attacker with access
               to a remote SSH_AUTH_SOCK from forwarding it again and
               using it on a different host (but only to a permitted

       -K      Load resident keys from a FIDO authenticator.

       -k      When loading keys into or deleting keys from the agent,
               process plain private keys only and skip certificates.

       -L      Lists public key parameters of all identities currently
               represented by the agent.

       -l      Lists fingerprints of all identities currently
               represented by the agent.

       -q      Be quiet after a successful operation.

       -S provider
               Specifies a path to a library that will be used when
               adding FIDO authenticator-hosted keys, overriding the
               default of using the internal USB HID support.

       -s pkcs11
               Add keys provided by the PKCS#11 shared library pkcs11.
               Certificate files may optionally be listed as command-
               line arguments.  If these are present, then they will be
               loaded into the agent using any corresponding private
               keys loaded from the PKCS#11 token.

       -T pubkey ...
               Tests whether the private keys that correspond to the
               specified pubkey files are usable by performing sign and
               verify operations on each.

       -t life
               Set a maximum lifetime when adding identities to an
               agent.  The lifetime may be specified in seconds or in a
               time format specified in sshd_config(5).

       -v      Verbose mode.  Causes to print debugging messages about
               its progress.  This is helpful in debugging problems.
               Multiple -v options increase the verbosity.  The maximum
               is 3.

       -X      Unlock the agent.

       -x      Lock the agent with a password.

ENVIRONMENT         top

               If needs a passphrase, it will read the passphrase from
               the current terminal if it was run from a terminal.  If
               does not have a terminal associated with it but DISPLAY
               and SSH_ASKPASS are set, it will execute the program
               specified by SSH_ASKPASS (by default “ssh-askpass”) and
               open an X11 window to read the passphrase.  This is
               particularly useful when calling from a .xsession or
               related script.

               SSH_ASKPASS_REQUIRE allows further control over the use
               of an askpass program.  If this variable is set to
               “never” then will never attempt to use one.  If it is set
               to “prefer”, then will prefer to use the askpass program
               instead of the TTY when requesting passwords.  Finally,
               if the variable is set to “force”, then the askpass
               program will be used for all passphrase input regardless
               of whether DISPLAY is set.

               Identifies the path of a Unix-domain socket used to
               communicate with the agent.

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

FILES         top

               Contains the DSA, ECDSA, authenticator-hosted ECDSA,
               Ed25519, authenticator-hosted Ed25519 or RSA
               authentication identity of the user.

       Identity files should not be readable by anyone but the user.
       Note that ignores identity files if they are accessible by

EXIT STATUS         top

       Exit status is 0 on success, 1 if the specified command fails,
       and 2 if is unable to contact the authentication agent.

SEE ALSO         top

       ssh(1), ssh-agent(1), ssh-askpass(1), ssh-keygen(1), 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.

COLOPHON         top

       This page is part of the openssh (Portable OpenSSH) project.
       Information about the project can be found at  If you have a bug report
       for this manual page, see ⟨⟩.
       This page was obtained from the tarball openssh-9.6p1.tar.gz
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       2023-12-22.  If you discover any rendering problems in this HTML
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GNU                         December 18, 2023                 SSH-ADD(1)