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)