mount: (adoc) add hint about /proc and /sys to --all description

Addresses: https://github.com/util-linux/util-linux/issues/1492
Signed-off-by: Karel Zak <kzak@redhat.com>

diff --git a/sys-utils/mount.8.adoc b/sys-utils/mount.8.adoc
index 8637f74dd917d31885454113daeb43bd2eacd039..c3c2e0dcf065f2e3a9b8ebd003992fd203dc7462 100644 (file)
--- a/sys-utils/mount.8.adoc
+++ b/sys-utils/mount.8.adoc
@@ -301,6 +301,8 @@ Command-line options available for the *mount* command are:
 *-a*, *--all*::
 Mount all filesystems (of the given types) mentioned in _fstab_ (except for those whose line contains the *noauto* keyword). The filesystems are mounted following their order in _fstab_. The *mount* command compares filesystem source, target (and fs root for bind mount or btrfs) to detect already mounted filesystems. The kernel table with already mounted filesystems is cached during *mount --all*. This means that all duplicated _fstab_ entries will be mounted.
 +
+The correct functionality depends on /proc (to detect already mounted filesystems) and on /sys (to evaluate filesystem tags like UUID= or LABEL=). It's strongly recommended to mount /proc and /sys filesystems before *mount -a* is executed on system boot.
++
 The option *--all* is possible to use for remount operation too. In this case all filters (*-t* and *-O*) are applied to the table of already mounted filesystems.
 +
 Since version 2.35 is possible to use the command line option *-o* to alter mount options from _fstab_ (see also *--options-mode*).