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NAME | SYNOPSIS | DESCRIPTION | OPTIONS | OUTPUT COLUMNS | FILTER EXAMPLES | COUNTER EXAMPLES | HISTORY | AUTHORS | SEE ALSO | REPORTING BUGS | AVAILABILITY |
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LSFD(1) User Commands LSFD(1)
lsfd - list file descriptors
lsfd [option]
lsfd is intended to be a modern replacement for lsof(8) on Linux
systems. Unlike lsof, lsfd is specialized to Linux kernel; it
supports Linux specific features like namespaces with simpler
code. lsfd is not a drop-in replacement for lsof; they are
different in the command line interface and output formats.
The default output is subject to change. So whenever possible, you
should avoid using default outputs in your scripts. Always
explicitly define expected columns by using --output columns-list
in environments where a stable output is required.
lsfd uses Libsmartcols for output formatting and filtering. See
the description of --output option for customizing the output
format, and --filter option for filtering. Use lsfd --list-columns
to get a list of all available columns.
-l, --threads
List in threads level.
-J, --json
Use JSON output format.
-n, --noheadings
Don’t print headings.
-o, --output list
Specify which output columns to print. See the OUTPUT COLUMNS
section for details of available columns.
The default list of columns may be extended if list is
specified in the format +list (e.g., lsfd -o +DELETED).
-r, --raw
Use raw output format.
--notruncate
Don’t truncate text in columns.
-p, --pid list
Collect information only for the specified processes. The list
is a comma-separated list of PIDs. See also FILTER EXAMPLES.
-i[4|6], --inet[=4|=6]
List only IPv4 sockets and/or IPv6 sockets.
-Q, --filter expression
Print only the files matching the condition represented by the
expression. See also scols-filter(5) and FILTER EXAMPLES.
The -Q option with a PID (for example: -Q PID==1) and the -p
option (for example: -p 1) can be used to achieve the same
result, but using the -p option is much more efficient because
it works at a much earlier stage of processing than the -Q
option.
-C, --counter label:filter_expr
Define a custom counter used in --summary output. lsfd makes a
counter named label. During collect information, lsfd counts
files matching filter_expr, and stores the counted number to
the counter named label. lsfd applies filters defined with
--filter options before counting; files excluded by the
filters are not counted.
See scols-filter(5) about filter_expr. label should not
include { nor :. You can define multiple counters by
specifying this option multiple times. See also COUNTER
EXAMPLES.
--summary[=mode]
This option controls summary lines output. The optional
argument mode can be only, append, or never. If the mode
argument is omitted, it defaults to only.
The summary reports counters. A counter consists of a label
and an integer value. --counter is the option for defining a
counter. If a user defines no counter, lsfd uses the
definitions of pre-defined built-in counters (default
counters) to make the summary output.
CAUTION: Using --summary and --json may make the output
broken. Only combining --summary=only and --json is valid.
--debug-filter
Dump the internal data structure for the filter and exit. This
is useful only for lsfd developers.
--dump-counters
Dump the definition of counters used in --summary output.
--hyperlink[=when]
Print paths as terminal hyperlinks. The optional when argument
can be always, never, or auto. If the argument is omitted, it
defaults to auto, which means that hyperlinks will only be
used when the output goes to a terminal.
-H, --list-columns
List the columns that can be specified with the --output
option. Can be used with --json or --raw to get the list in a
machine-readable format.
-h, --help
Display help text and exit.
-V, --version
Display version and exit.
Each column has a type. Types are surround by < and >.
CAUTION: The names and types of columns are not stable yet. They
may be changed in the future releases.
AINODECLASS <string>
Class of anonymous inode.
ASSOC <string>
Association between file and process.
BLKDRV <string>
Block device driver name resolved by /proc/devices.
BPF-MAP.ID <number>
Bpf map ID.
BPF-MAP.TYPE <string>
Decoded name of bpf map type.
BPF-MAP.TYPE.RAW <number>
Bpf map type (raw).
BPF.NAME <string>
Bpf object name.
BPF-PROG.ID <number>
Bpf program ID.
BPF-PROG.TAG <string>
Bpf program TAG.
BPF-PROG.TYPE <string>
Decoded name of bpf program type.
BPF-PROG.TYPE.RAW <number>
Bpf program type (raw).
CHRDRV <string>
Character device driver name resolved by /proc/devices.
COMMAND <string>
Command of the process opening the file.
DELETED <boolean>
Reachability from the file system.
DEV <string>
ID of the device containing the file.
DEVTYPE <string>
Device type (blk, char, or nodev).
ENDPOINTS <string>
IPC endpoints information communicated with the fd.
lsfd collects endpoints within the processes that lsfd scans;
lsfd may miss some endpoints if you limits the processes with
-p option.
The format of the column depends on the object associated with
the fd:
FIFO type, mqueue type, ptmx and pts sources
PID,COMMAND,ASSOC[-r][-w]
The last characters ([-r][-w]) represent the read and/or
write mode of the endpoint.
eventfd type
PID,COMMAND,ASSOC
UNIX
Same as UNIX-STREAM.
In a container, lsfd may not fill ENDPOINTS column. lsfd
uses sock_diag(7) to collect information about UNIX
endpoints. SELinux may limit the use sock_diag in a
container. You can remove the limit by setting 1 to
virt_sandbox_use_netlink bool. See container_selinux(8)
for more details.
UNIX-STREAM
PID,COMMAND,ASSOC[-r?][-w?]
About the last characters ([-r?][-w?]), see the
description of SOCK.SHUTDOWN.
EVENTFD.ID <number>
Eventfd ID.
EVENTPOLL.TFDS <string>
File descriptors targeted by the eventpoll file.
FD <number>
File descriptor for the file.
FLAGS <string>
Flags specified when opening the file.
FUID <number>
User ID number of the file’s owner.
INET.LADDR <string>
Local IP address.
INET.RADDR <string>
Remote IP address.
INET6.LADDR <string>
Local IP6 address.
INET6.RADDR <string>
Remote IP6 address.
INODE <number>
Inode number.
INOTIFY.INODES <string>
Cooked version of INOTIFY.INODES.RAW. The format of the
element is inode-number,source-of-inode.
INOTIFY.INODES.RAW <string>
List of monitoring inodes. The format of the element is
inode-number,device-major:device-minor.
KNAME <string>
Raw file name extracted from from /proc/pid/fd/fd or
/proc/pid/map_files/region.
KTHREAD <boolean>
Whether the process is a kernel thread or not.
MAJ:MIN <string>
Device ID for special, or ID of device containing file.
MAPLEN <number>
Length of file mapping (in page).
MISCDEV <string>
Misc character device name resolved by /proc/misc.
MNTID <number>
Mount ID.
MODE <string>
Access mode (rwx).
NAME <string>
Cooked version of KNAME. It is mostly same as KNAME.
Some files have special formats and information sources:
AF_VSOCK
state=SOCK.STATE type=SOCK.TYPE laddr=VSOCK.LADDR[
raddr=VSOCK.RADDR]
raddr is not shown for listening sockets.
bpf-map
id=BPF-MAP.ID type=BPF-MAP.TYPE[ name=BPF.NAME]
bpf-prog
id=BPF-PROG.ID type=BPF-PROG.TYPE tag= BPF-PROG.TAG [
name=BPF.NAME]
eventpoll
tfds=EVENTPOLL.TFDS
eventfd
id=EVENTFD.ID
inotify
inodes=INOTIFY.INODES
misc:tun
iface=TUN.IFACE
NETLINK
protocol=NETLINK.PROTOCOL[ lport=NETLINK.LPORT[
group=NETLINK.GROUPS]]
PACKET
type=SOCK.TYPE[ protocol=PACKET.PROTOCOL][
iface=PACKET.IFACE]
pidfd
pid=TARGET-PID comm=TARGET-COMMAND nspid=TARGET-NSPIDS
lsfd extracts TARGET-PID and TARGET-NSPIDS from
/proc/pid/fdinfo/fd.
PING
state=SOCK.STATE[ id=PING.ID][ laddr=INET.LADDR [
raddr=INET.RADDR]]
PINGv6
state=SOCK.STATE[ id=PING.ID][ laddr=INET6.LADDR [
raddr=INET6.RADDR]]
ptmx
tty-index=PTMX.TTY-INDEX
lsfd extracts PTMX.TTY-INDEX from /proc/pid/fdinfo/fd.
RAW
state=SOCK.STATE[ protocol=RAW.PROTOCOL [ laddr=INET.LADDR
[ raddr=INET.RADDR]]]
RAWv6
state=SOCK.STATE[ protocol=RAW.PROTOCOL [
laddr=INET6.LADDR [ raddr=INET6.RADDR]]]
signalfd
mask=SIGNALFD.MASK
TCP, TCPv6
state=SOCK.STATE[ laddr=TCP.LADDR [ raddr=TCP.RADDR]]
timerfd
clockid=TIMERFD.CLOCKID[ remaining=TIMERFD.REMAINING [
interval=TIMERFD.INTERVAL]]
UDP, UDPv6
state=SOCK.STATE[ laddr=UDP.LADDR [ raddr=UDP.RADDR]]
lsfd hides raddr= if UDP.RADDR is 0.0.0.0 and UDP.RPORT is
0.
UDP-LITE, UDPLITEv6
state=SOCK.STATE[ laddr=UDPLITE.LADDR [
raddr=UDPLITE.RADDR]]
UNIX-STREAM
state=SOCK.STATE[ path=UNIX.PATH]
UNIX
state=SOCK.STATE[ path=UNIX.PATH] type=SOCK.TYPE
Note that (deleted) markers are removed from this column.
Refer to KNAME, DELETED, or XMODE to know the readability
of the file from the file system.
NETLINK.GROUPS <number>
Netlink multicast groups.
NETLINK.LPORT <number>
Netlink local port id.
NETLINK.PROTOCOL <string>
Netlink protocol.
NLINK <number>
Link count.
NS.NAME <string>
Name (NS.TYPE:[INODE]) of the namespace specified with the
file.
NS.TYPE <string>
Type of the namespace specified with the file. The type is
mnt, cgroup, uts, ipc, user, pid, net, time, or unknown.
OWNER <string>
Owner of the file.
PACKET.IFACE <string>
Interface name associated with the packet socket.
PACKET.PROTOCOL <string>
L2 protocol name associated with the packet socket (decoded).
PACKET.PROTOCOL.RAW <number>
L2 protocol number associated with the packet socket (raw).
PARTITION <string>
Block device name resolved by /proc/partition.
PID <number>
PID of the process opening the file.
PIDFD.COMM <string>
Command of the process targeted by the pidfd.
PIDFD.NSPID <string>
Value of NSpid field in /proc/pid/fdinfo/fd of the pidfd.
Quoted from kernel/fork.c of Linux source tree:
If pid namespaces are supported then this function
will also print the pid of a given pidfd refers to
for all descendant pid namespaces starting from the
current pid namespace of the instance, i.e. the Pid
field and the first entry in the NSpid field will be
identical.
Note that this differs from the Pid and NSpid fields
in /proc/<pid>/status where Pid and NSpid are always
shown relative to the pid namespace of the procfs
instance.
PIDFD.PID <number>
PID of the process targeted by the pidfd.
PING.ID <`number`>
ICMP echo request id used on the PING socket.
POS <number>
File position.
RAW.PROTOCOL <number>
Protocol number of the raw socket.
RDEV <string>
Device ID (if special file).
SIGNALFD.MASK <string>
Masked signals.
SIZE <number>
File size.
SOCK.LISTENING <boolean>
Listening socket.
SOCK.NETS <number>
Inode identifying network namespace where the socket belongs
to.
SOCK.PROTONAME <string>
Protocol name.
SOCK.SHUTDOWN <string>
Shutdown state of socket.
[-r?]
If the first character is r, the receptions are allowed.
If it is -, the receptions are disallowed. If it is ?, the
state is unknown.
[-w?]
If the second character is w, the transmissions are
allowed. If it is -, the transmissions are disallowed. If
it is ?, the state is unknown.
SOCK.STATE <string>
State of socket.
SOCK.TYPE <string>
Type of socket. Here type means the second parameter of socket
system call:
• stream
• dgram
• raw
• rdm
• seqpacket
• dccp
• packet
SOURCE <string>
File system, partition, or device containing the file. For the
association having ERROR as the value for TYPE column, lsfd
fills this column with syscall:_errno_.
STTYPE <string>
Raw file types returned from stat(2): BLK, CHR, DIR, FIFO,
LINK, REG, SOCK, or UNKN.
TCP.LADDR <string>
Local L3 (INET.LADDR or INET6.LADDR) address and local TCP
port.
TCP.LPORT <number>
Local TCP port.
TCP.RADDR <string>
Remote L3 (INET.RADDR or INET6.RADDR) address and remote TCP
port.
TCP.RPORT <number>
Remote TCP port.
TID <number>
Thread ID of the process opening the file.
TIMERFD.CLOCKID <string>
Clockid.
TIMERFD.INTERVAL <number>
Interval.
TIMERFD.REMAINING <number>
Remaining time.
PTMX.TTY-INDEX <number>
TTY index of the counterpart.
TUN.IFACE <string>
Network interface behind the tun device.
TYPE <string>
Cooked version of STTYPE. It is same as STTYPE with
exceptions. For SOCK, print the value for SOCK.PROTONAME. For
UNKN, print the value for AINODECLASS if SOURCE is
anon_inodefs.
If lsfd gets an error when calling a syscall to know about a
target file descriptor, lsfd fills this column for it with
ERROR.
UDP.LADDR <string>
Local IP address and local UDP port.
UDP.LPORT <number>
Local UDP port.
UDP.RADDR <string>
Remote IP address and remote UDP port.
UDP.RPORT <number>
Remote UDP port.
UDPLITE.LADDR <string>
Local IP address and local UDPLite port.
UDPLITE.LPORT <number>
Local UDP port.
UDPLITE.RADDR <string>
Remote IP address and remote UDPLite port.
UDPLITE.RPORT <number>
Remote UDP port.
UID <number>
User ID number.
UNIX.IPEER < number >
Inode number for the peer of the UNIX domain socket.
If lsfd runs in a container, it may not fill UNIX.IPEER
column. See the description of UNIX in ENDPOINTS column for
more details.
UNIX.PATH <string>
Filesystem pathname for UNIX domain socket.
USER <string>
User of the process.
VSOCK.LADDR <string>, VSOCK.RADDR <string>
Local VSOCK address. The format of the element is
VSOCK.LCID:VSOCK.LPORT.
Well-known CIDs will be decoded: “*”, “hypervisor”, “local”,
or “host”. Well-known ports will be decoded: “*”.
VSOCK.LCID <number>, VSOCK.RCID <number>
Local and remote VSOCK context identifiers.
VSOCK.LPORT <number>, VSOCK.RPORT <number>
Local and remote VSOCK ports.
XMODE <string>
Extended version of MODE. This column may grow; new letters
may be appended to XMODE when lsfd supports a new state of
file descriptors and/or memory mappings.
[-r]
opened of mapped for reading. This is also in MODE.
[-w]
opened of mapped for writing. This is also in MODE.
[-x]
mapped for executing the code. This is also in MODE.
[-D]
deleted from the file system. See also DELETED.
[-Ll]
locked or leased. l represents a read, a shared lock or a
read lease. L represents a write or an exclusive lock or a
write lease. If both read/shared and write/exclusive locks
or leases are taken by a file descriptor, L is used as the
flag.
[-m]
Multiplexed. If the file descriptor is targeted by a
eventpoll file or classical system calls for multiplexing
(select, pselect, poll, and ppoll), this bit flag is set.
Note that if an invocation of the classical system calls
is interrupted, lsfd may fail to mark m on the file
descriptors monitored by the invocation. See
restart_syscall(2).
lsfd has few options for filtering. In most of cases, what you
should know is -Q (or --filter) option. Combined with -o (or
--output) option, you can customize the output as you want.
List files associated with PID 1 and PID 2 processes:
# lsfd -Q '(PID == 1) or (PID == 2)'
Do the same in an alternative way:
# lsfd -Q '(PID == 1) || (PID == 2)'
Do the same in a more efficient way:
# lsfd --pid 1,2
Whitespaces can be used instead of a comma:
# lsfd --pid '1 2'
Utilize pidof(1) for list the files associated with "firefox":
# lsfd --pid "$(pidof firefox)"
List the 1st file descriptor opened by PID 1 process:
# lsfd -Q '(PID == 1) and (FD == 1)'
Do the same in an alternative way:
# lsfd -Q '(PID == 1) && (FD == 1)'
List all running executables:
# lsfd -Q 'ASSOC == "exe"'
Do the same in an alternative way:
# lsfd -Q 'ASSOC eq "exe"'
Do the same but print only file names:
# lsfd -o NAME -Q 'ASSOC eq "exe"' | sort -u
List deleted files associated to processes:
# lsfd -Q 'DELETED'
List non-regular files:
# lsfd -Q 'TYPE != "REG"'
List block devices:
# lsfd -Q 'DEVTYPE == "blk"'
Do the same with TYPE column:
# lsfd -Q 'TYPE == "BLK"'
List files including "dconf" directory in their names:
# lsfd -Q 'NAME =~ ".\*/dconf/.*"'
List files opened in a QEMU virtual machine:
# lsfd -Q '(COMMAND =~ ".\*qemu.*") and (FD >= 0)'
List timerfd files expired within 0.5 seconds:
# lsfd -Q '(TIMERFD.remaining < 0.5) and (TIMERFD.remaining > 0.0)'
List processes communicating via unix stream sockets:
# lsfd -Q 'TYPE == "UNIX-STREAM" && UNIX.PATH =~ ".+"' -oUNIX.PATH,PID,COMMAND,FD,SOCK.STATE,ENDPOINTS
List processes communicating via a specified unix stream socket:
# lsfd -Q 'TYPE == "UNIX-STREAM" && UNIX.PATH == "@/tmp/.X11-unix/X0"' -oUNIX.PATH,PID,COMMAND,FD,SOCK.STATE,ENDPOINTS
Report the numbers of netlink socket descriptors and unix socket
descriptors:
# lsfd --summary=only \
-C 'netlink sockets':'(NAME =~ "NETLINK:.*")' \
-C 'unix sockets':'(NAME =~ "UNIX:.*")'
VALUE COUNTER
57 netlink sockets
1552 unix sockets
Do the same but print in JSON format:
# lsfd --summary=only --json \
-C 'netlink sockets':'(NAME =~ "NETLINK:.*")' \
-C 'unix sockets':'(NAME =~ "UNIX:.*")'
{
"lsfd-summary": [
{
"value": 15,
"counter": "netlink sockets"
},{
"value": 798,
"counter": "unix sockets"
}
]
}
The lsfd command is part of the util-linux package since v2.38.
Masatake YAMATO <yamato@redhat.com>, Karel Zak <kzak@redhat.com>
bpftool(8), bps(8), lslocks(8), lsof(8), pidof(1), proc(5),
scols-filter(5), socket(2), ss(8), stat(2), vsock(7)
For bug reports, use the issue tracker
<https://github.com/util-linux/util-linux/issues>.
The lsfd command is part of the util-linux package which can be
downloaded from Linux Kernel Archive
<https://www.kernel.org/pub/linux/utils/util-linux/>. This page is
part of the util-linux (a random collection of Linux utilities)
project. Information about the project can be found at
⟨https://www.kernel.org/pub/linux/utils/util-linux/⟩. If you have a
bug report for this manual page, send it to
util-linux@vger.kernel.org. This page was obtained from the
project's upstream Git repository
⟨git://git.kernel.org/pub/scm/utils/util-linux/util-linux.git⟩ on
2025-08-11. (At that time, the date of the most recent commit that
was found in the repository was 2025-08-05.) 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
util-linux 2.42-start-521-ec46 2025-08-09 LSFD(1)
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HTML rendering created 2025-09-06 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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