proc_pid(5)                   File Formats Manual                  proc_pid(5)

NAME
       /proc/pid/, /proc/self/ - process information

DESCRIPTION
       /proc/pid/
              There is a numerical subdirectory for each running process; the
              subdirectory is named by the process ID.  Each /proc/pid
              subdirectory contains the pseudo-files and directories described
              below.

              The files inside each /proc/pid directory are normally owned by
              the effective user and effective group ID of the process.
              However, as a security measure, the ownership is made root:root
              if the process's "dumpable" attribute is set to a value other
              than 1.

              Before Linux 4.11, root:root meant the "global" root user ID and
              group ID (i.e., UID 0 and GID 0 in the initial user namespace).
              Since Linux 4.11, if the process is in a noninitial user
              namespace that has a valid mapping for user (group) ID 0 inside
              the namespace, then the user (group) ownership of the files
              under /proc/pid is instead made the same as the root user
              (group) ID of the namespace.  This means that inside a
              container, things work as expected for the container "root"
              user.

              The process's "dumpable" attribute may change for the following
              reasons:

              o  The attribute was explicitly set via the prctl(2)
                 PR_SET_DUMPABLE operation.

              o  The attribute was reset to the value in the file
                 /proc/sys/fs/suid_dumpable (described below), for the reasons
                 described in prctl(2).

              Resetting the "dumpable" attribute to 1 reverts the ownership of
              the /proc/pid/* files to the process's effective UID and GID.
              Note, however, that if the effective UID or GID is subsequently
              modified, then the "dumpable" attribute may be reset, as
              described in prctl(2).  Therefore, it may be desirable to reset
              the "dumpable" attribute after making any desired changes to the
              process's effective UID or GID.

       /proc/self/
              This directory refers to the process accessing the /proc
              filesystem, and is identical to the /proc directory named by the
              process ID of the same process.

SEE ALSO
       proc(5)

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