listmount(2) - Linux manual page (original) (raw)

listmount(2) System Calls Manual listmount(2)

NAME top

   listmount - get a list of mount ID's

LIBRARY top

   Standard C library (_libc_, _-lc_)

SYNOPSIS top

   **#include <linux/mount.h>** /* Definition of struct mnt_id_req constants */
   **#include <unistd.h>**

   **int syscall(SYS_listmount, struct mnt_id_req ***_req_**,**
               **uint64_t ***_mntids_**, size_t** _nrmntids_**,**
               **unsigned long** _flags_**);**

   **#include <linux/mount.h>**

   **struct mnt_id_req {**
       **__u32  size;** /* sizeof(struct mnt_id_req) */
       **__u64  mnt_id;** /* The parent mnt_id being searched */
       **__u64  param;** /* The next mnt_id we want to find */
   **};**

   _Note_: glibc provides no wrapper for **listmount**(), necessitating the
   use of [syscall(2)](../man2/syscall.2.html).

DESCRIPTION top

   To access the mounts in your namespace, you must have
   CAP_SYS_ADMIN in the user namespace.

   This function returns a list of mount IDs under the **req.mnt_id**.
   This is meant to be used in conjuction with [statmount(2)](../man2/statmount.2.html) in order
   to provide a way to iterate and discover mounted file systems.

The mnt_id_req structure req.size is used by the kernel to determine which struct mntidreq is being passed in, it should always be set to sizeof(struct mntidreq).

   _req.mntid_ is the parent mnt_id that we will list from, which can
   either be **LSMT_ROOT** which means the root mount of the current
   mount namespace, or a mount ID obtained from either [statx(2)](../man2/statx.2.html) using
   **STATX_MNT_ID_UNIQUE** or from [listmount(2)](../man2/listmount.2.html).

   _req.param_ is used to tell the kernel what mount ID to start the
   list from.  This is useful if multiple calls to [listmount(2)](../man2/listmount.2.html) are
   required.  This can be set to the last mount ID returned in order
   to resume from a previous spot in the list.

RETURN VALUE top

   On success, the number of entries filled into _mntids_ is returned;
   0 if there are no more mounts left.  On error, -1 is returned, and
   _[errno](../man3/errno.3.html)_ is set to indicate the error.

ERRORS top

   **EPERM** Permission is denied for accessing this mount.

   **EFAULT** _req_ or _mntids_ points to a location outside the process's
          accessible address space.

   **EINVAL** Invalid flag specified in _flags_.

   **EINVAL** _req_ is of insufficient size to be utilized.

   **E2BIG** _req_ is too large, the limit is the architectures page size.

   **ENOENT** The specified _req.mntid_ doesn't exist.

   **ENOMEM** Out of memory (i.e., kernel memory).

STANDARDS top

   Linux.

COLOPHON top

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Linux man-pages 6.10 2024-11-17 listmount(2)

Pages that refer to this page:listmount(2), statmount(2), statx(2)