proc_locks(5)                 File Formats Manual                proc_locks(5)

NAME
       /proc/locks - current file locks and leases

DESCRIPTION
       /proc/locks
              This file shows current file locks (flock(2) and fcntl(2)) and
              leases (fcntl(2)).

              An example of the content shown in this file is the following:

                  1: POSIX  ADVISORY  READ  5433 08:01:7864448 128 128
                  2: FLOCK  ADVISORY  WRITE 2001 08:01:7864554 0 EOF
                  3: FLOCK  ADVISORY  WRITE 1568 00:2f:32388 0 EOF
                  4: POSIX  ADVISORY  WRITE 699 00:16:28457 0 EOF
                  5: POSIX  ADVISORY  WRITE 764 00:16:21448 0 0
                  6: POSIX  ADVISORY  READ  3548 08:01:7867240 1 1
                  7: POSIX  ADVISORY  READ  3548 08:01:7865567 1826 2335
                  8: OFDLCK ADVISORY  WRITE -1 08:01:8713209 128 191

              The fields shown in each line are as follows:

              [1]  The ordinal position of the lock in the list.

              [2]  The lock type.  Values that may appear here include:

                   FLOCK  This is a BSD file lock created using flock(2).

                   OFDLCK This is an open file description (OFD) lock created
                          using fcntl(2).

                   POSIX  This is a POSIX byte-range lock created using
                          fcntl(2).

              [3]  Among the strings that can appear here are the following:

                   ADVISORY
                          This is an advisory lock.

                   MANDATORY
                          This is a mandatory lock.

              [4]  The type of lock.  Values that can appear here are:

                   READ   This is a POSIX or OFD read lock, or a BSD shared
                          lock.

                   WRITE  This is a POSIX or OFD write lock, or a BSD
                          exclusive lock.

              [5]  The PID of the process that owns the lock.

                   Because OFD locks are not owned by a single process (since
                   multiple processes may have file descriptors that refer to
                   the same open file description), the value -1 is displayed
                   in this field for OFD locks.  (Before Linux 4.14, a bug
                   meant that the PID of the process that initially acquired
                   the lock was displayed instead of the value -1.)

              [6]  Three colon-separated subfields that identify the major and
                   minor device ID of the device containing the filesystem
                   where the locked file resides, followed by the inode number
                   of the locked file.

              [7]  The byte offset of the first byte of the lock.  For BSD
                   locks, this value is always 0.

              [8]  The byte offset of the last byte of the lock.  EOF in this
                   field means that the lock extends to the end of the file.
                   For BSD locks, the value shown is always EOF.

              Since Linux 4.9, the list of locks shown in /proc/locks is
              filtered to show just the locks for the processes in the PID
              namespace (see pid_namespaces(7)) for which the /proc filesystem
              was mounted.  (In the initial PID namespace, there is no
              filtering of the records shown in this file.)

              The lslocks(8) command provides a bit more information about
              each lock.

SEE ALSO
       proc(5)

Linux man-pages 6.9.1             2024-05-02                     proc_locks(5)