man > proc_pid(5)

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 directo‐
              ries 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:

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

              •  The  attribute  was  reset to the value in the file /proc/sys/fs/suid_dumpable (de‐
                 scribed 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 6.7                          2023-08-15                                  proc_pid(5)