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proc_pid_root

Section: File Formats (5)
Updated: 2024-05-02
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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)

 

Index

NAME
DESCRIPTION
SEE ALSO
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Time: 11:48:46 GMT, September 14, 2026