Environment Variables, Files, History, Bugs, Authors, and References

libmount tries to be smart and use classic mount(2) only for well-known issues. If the new mount API is unavailable, libmount can still use traditional mount(2), although LIBMOUNT_FORCE_MOUNT2 is set to never. LIBMOUNT_FSTAB=<path> overrides the default location of the fstab file (ignored for suid) LIBMOUNT_DEBUG=all enables libmount debug output LIBBLKID_DEBUG=all enables libblkid debug output LOOPDEV_DEBUG=all enables loop device setup debug output FILES See also "The files /etc/fstab, /etc/mtab and /proc/mounts" section above. /etc/fstab filesystem table /run/mount libmount private runtime directory /etc/mtab table of mounted filesystems or symlink to /proc/mounts /etc/mtab~ lock file (unused on systems with mtab symlink) /etc/mtab.tmp temporary file (unused on systems with mtab symlink) /etc/filesystems a list of filesystem types to try HISTORY A mount command existed in Version 5 AT&T UNIX. BUGS It is possible for a corrupted filesystem to cause a crash. Some Linux filesystems don’t support -o sync and -o dirsync (the ext2, ext3, ext4, fat and vfat filesystems do support synchronous updates (a la BSD) when mounted with the sync option). The -o remount may not be able to change mount parameters (all ext2fs-specific parameters, except sb, are changeable with a remount, for example, but you can’t change gid or umask for the fatfs). It is possible that the files /etc/mtab and /proc/mounts don’t match on systems with a regular mtab file. The first file is based only on the mount command options, but the content of the second file also depends on the kernel and others settings (e.g. on a remote NFS server — in certain cases the mount command may report unreliable information about an NFS mount point and the /proc/mount file usually contains more reliable information.) This is another reason to replace the mtab file with a symlink to the /proc/mounts file. Checking files on NFS filesystems referenced by file descriptors (i.e. the fcntl and ioctl families of functions) may lead to inconsistent results due to the lack of a consistency check in the kernel even if the noac mount option is used. The loop option with the offset or sizelimit options used may fail when using older kernels if the mount command can’t confirm that the size of the block device has been configured as requested. This situation can be worked around by using the losetup(8) command manually before calling mount with the configured loop device. AUTHORS Karel Zak <kzak@redhat.com> SEE ALSO mount(2), umount(2), filesystems(5), fstab(5), nfs(5), xfs(5), mount_namespaces(7), xattr(7), e2label(8), findmnt(8), losetup(8), lsblk(8), mke2fs(8), mountd(8), nfsd(8), swapon(8), tune2fs(8), umount(8), xfs_admin(8) REPORTING BUGS For bug reports, use the issue tracker at https://github.com/util-linux/util-linux/issues. AVAILABILITY The mount command is part of the util-linux package which can be downloaded from Linux Kernel Archive <https://www.kernel.org/pub/linux/utils/util-linux/>. util-linux 2.39.1 2023‐06‐27 MOUNT(8)

This section continues from the previous one, detailing several environment variables like `LIBMOUNT_FSTAB`, `LIBMOUNT_DEBUG`, `LIBBLKID_DEBUG`, and `LOOPDEV_DEBUG` that control `libmount`'s behavior. It lists important files such as `/etc/fstab`, `/run/mount`, and `/etc/mtab` and their functions. It briefly touches on the history of the `mount` command, mentions known bugs (e.g., potential crashes with corrupted filesystems, issues with `-o sync` and `-o dirsync`, and discrepancies between `/etc/mtab` and `/proc/mounts`), identifies the author, and lists related commands and documentation for further reference.