proc_pid(5) — Linux manual page

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:

              •  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 (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)

COLOPHON

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

Pages that refer to this page: PR_SET_DUMPABLE(2const)

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