NAME

       /proc/pid/root/ - symbolic link to root directory

DESCRIPTION

       /proc/pid/root/
              UNIX  and  Linux  support  the  idea of a per-process root of the filesystem, set by the chroot(2)
              system call.  This file is a symbolic link that  points  to  the  process's  root  directory,  and
              behaves in the same way as exe, and fd/*.

              Note  however  that  this  file  is  not merely a symbolic link.  It provides the same view of the
              filesystem (including namespaces and the set of per-process mounts) as  the  process  itself.   An
              example  illustrates  this  point.   In  one  terminal,  we  start  a  shell in new user and mount
              namespaces, and in that shell we create some new mounts:

                  $ PS1='sh1# ' unshare -Urnm
                  sh1# mount -t tmpfs tmpfs /etc  # Mount empty tmpfs at /etc
                  sh1# mount --bind /usr /dev     # Mount /usr at /dev
                  sh1# echo $$
                  27123

              In a second terminal window, in the initial mount namespace,  we  look  at  the  contents  of  the
              corresponding mounts in the initial and new namespaces:

                  $ PS1='sh2# ' sudo sh
                  sh2# ls /etc | wc -l                  # In initial NS
                  309
                  sh2# ls /proc/27123/root/etc | wc -l  # /etc in other NS
                  0                                     # The empty tmpfs dir
                  sh2# ls /dev | wc -l                  # In initial NS
                  205
                  sh2# ls /proc/27123/root/dev | wc -l  # /dev in other NS
                  11                                    # Actually bind
                                                        # mounted to /usr
                  sh2# ls /usr | wc -l                  # /usr in initial NS
                  11

              In  a multithreaded process, the contents of the /proc/pid/root symbolic link are not available if
              the main thread has already terminated (typically by calling pthread_exit(3)).

              Permission to dereference or read (readlink(2)) this symbolic link is governed by a ptrace  access
              mode PTRACE_MODE_READ_FSCREDS check; see ptrace(2).

SEE ALSO

       proc(5)