lsfd(1) — Linux manual page


LSFD(1)                       User Commands                      LSFD(1)

NAME         top

       lsfd - list file descriptors

SYNOPSIS         top

       lsfd [option]

DESCRIPTION         top

       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.

OPTIONS         top

       -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.

           Don’t truncate text in columns.

       -p, --pid pids
           Collect information only for specified processes. pids is a
           list of pids. A comma or whitespaces can be used as
           separators. You can use this option with pidof(1). See FILTER

           Both -Q option with an expression including PID, e.g. -Q (PID
           == 1), and -p option, e.g. -p 1, may print the same output
           but using -p option is much more efficient because -p option
           works at a much earlier stage of processing than the -Q

       -i[4|6], --inet[=4|=6]
           List only IPv4 sockets and/or IPv6 sockets.

       -Q, --filter expr
           Print only the files matching the condition represented by
           the expr. See also scols-filter(5) and FILTER EXAMPLES.

       -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.

           This option controls summary lines output. The optional
           argument when can be only, append or never. If the when
           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.

           Dump the internal data structure for the filter and exit.
           This is useful only for lsfd developers.

           Dump the definition of counters used in --summary output.

       -H, --list-columns
           List available columns that you can specify at --output

       -h, --help
           Display help text and exit.

       -V, --version
           Print version and exit.

OUTPUT COLUMNS         top

       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.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).

       ENDPOINT <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

               The last characters ([-r][-w]) represents the read and/or
               write mode of the endpoint.

           eventfd type


               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

       KNAME <string>
           Raw file name extracted from from /proc/pid/fd/fd or

       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:

               id=BPF-MAP.ID type=BPF-MAP.TYPE[ name=BPF.NAME]

               id=BPF-PROG.ID type=BPF-PROG.TYPE[ name=BPF.NAME]





               protocol=NETLINK.PROTOCOL[ lport=NETLINK.LPORT[

               type=SOCK.TYPE[ protocol=PACKET.PROTOCOL][

               pid=TARGET-PID comm=TARGET-COMMAND nspid=TARGET-NSPIDS

               lsfd extracts TARGET-PID and TARGET-NSPIDS from

               state=SOCK.STATE[ id=PING.ID][ laddr=INET.LADDR [

               state=SOCK.STATE[ id=PING.ID][ laddr=INET6.LADDR [


               lsfd extracts PTMX.TTY-INDEX from /proc/pid/fdinfo/fd.

               state=SOCK.STATE[ protocol=RAW.PROTOCOL [
               laddr=INET.LADDR [ raddr=INET.RADDR]]]

               state=SOCK.STATE[ protocol=RAW.PROTOCOL [
               laddr=INET6.LADDR [ raddr=INET6.RADDR]]]


           TCP, TCPv6
               state=SOCK.STATE[ laddr=TCP.LADDR [ raddr=TCP.RADDR]]

               clockid=TIMERFD.CLOCKID[ remaining=TIMERFD.REMAINING [

           UDP, UDPv6
               state=SOCK.STATE[ laddr=UDP.LADDR [ raddr=UDP.RADDR]]

               lsfd hides raddr= if UDP.RADDR is and UDP.RPORT
               is 0.

           UDP-LITE, UDPLITEv6
               state=SOCK.STATE[ laddr=UDPLITE.LADDR [

               state=SOCK.STATE[ path=UNIX.PATH]

               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

       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>
           L3 protocol associated with the packet socket.

       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

              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

       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

       SOCK.PROTONAME <string>
           Protocol name.

       SOCK.SHUTDOWN <string>
           Shutdown state of socket.

               If the first character is r, the receptions are allowed.
               If it is -, the receptions are disallowed. If it is ?,
               the state is unknown.

               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.

       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

       TCP.LPORT <number>
           Local TCP port.

       TCP.RADDR <string>
           Remote L3 (INET.RADDR or INET6.RADDR) address and remote TCP

       TCP.RPORT <number>
           Remote TCP port.

       TID <number>
           Thread ID of the process opening the file.

       TIMERFD.CLOCKID <string>

       TIMERFD.INTERVAL <number>

       TIMERFD.REMAINING <number>
           Remaining time.

       PTMX.TTY-INDEX <number>
           TTY index of the counterpart.

       TUN.IFACE <string>
           Network intrface 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

       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.PATH <string>
           Filesystem pathname for UNIX domain socket.

       USER <string>
           User of the process.

       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.

               opened of mapped for reading. This is also in MODE.

               opened of mapped for writing. This is also in MODE.

               mapped for executing the code. This is also in MODE.

               deleted from  the file system. See also DELETED..

               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.

               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 invocaiton of the classical system calls
               is interrupted, lsfd may fail to mark m on the file
               descriptors monitored by the invocaiton. See


       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

       Whitescapes 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)'

       Hide files associated to kernel threads:

           # lsfd -Q '!KTHREAD'

       List timerfd files expired within 0.5 seconds:

           # lsfd -Q '(TIMERFD.remaining < 0.5) and (TIMERFD.remaining > 0.0)'


       Report the numbers of netlink socket descriptors and unix socket

           # 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"

HISTORY         top

       The lsfd command is part of the util-linux package since v2.38.

AUTHORS         top

       Masatake YAMATO <>, Karel Zak <>

SEE ALSO         top

       bpftool(8) bps(8) lslocks(8) lsof(8) pidof(1) proc(5)
       scols-filter(5) socket(2) ss(8) stat(2)

REPORTING BUGS         top

       For bug reports, use the issue tracker at

AVAILABILITY         top

       The lsfd command is part of the util-linux package which can be
       downloaded from Linux Kernel Archive
       <>. This page
       is part of the util-linux (a random collection of Linux
       utilities) project. Information about the project can be found at
       ⟨⟩. If you have
       a bug report for this manual page, send it to This page was obtained from the
       project's upstream Git repository
       ⟨git://⟩ on
       2023-12-22. (At that time, the date of the most recent commit
       that was found in the repository was 2023-12-14.) 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

util-linux 2.39.1041-8a7c      2023-12-22                        LSFD(1)