Check fs-ro

Overview

Checks for unexpectedly read-only mounted filesystems, such as a root filesystem that switched to read-only due to disk errors. Ignores ramfs, squashfs (snapd), and other pseudo-filesystems by default. Additional mount points can be excluded via --ignore. Alerts when a read-only filesystem is detected that should be writable.

Data Collection:

  • Reads /proc/mounts and checks the mount options for each entry

  • Skips ramfs and squashfs filesystem types entirely

  • Skips mount points whose path starts with any --ignore prefix (default: /dev/loop, /proc, /run/credentials, /snap, /sys/fs)

Fact Sheet

Fact

Value

Check Plugin Download

https://github.com/Linuxfabrik/monitoring-plugins/tree/main/check-plugins/fs-ro

Nagios/Icinga Check Name

check_fs_ro

Check Interval Recommendation

Every 15 minutes

Can be called without parameters

Yes

Runs on

Linux

Compiled for Windows

No

Help

usage: fs-ro [-h] [-V] [--always-ok] [--ignore IGNORE] [--test TEST]

Checks for unexpectedly read-only mounted filesystems, such as a root
filesystem that switched to read-only due to disk errors. Ignores ramfs,
squashfs (snapd), and other pseudo-filesystems by default. Additional
mountpoints can be excluded via --ignore. Alerts when a read-only filesystem
is detected that should be writable.

options:
  -h, --help       show this help message and exit
  -V, --version    show program's version number and exit
  --always-ok      Always returns OK.
  --ignore IGNORE  Mount point prefix to ignore. All mount points starting
                   with this value will be skipped. Can be specified multiple
                   times. Example: `--ignore /sys/fs` ignores `/sys/fs/cgroup`
                   and similar. Default: /dev/loop, /proc, /run/credentials,
                   /snap, /sys/fs.
  --test TEST      For unit tests. Needs "path-to-stdout-file,path-to-stderr-
                   file,expected-retc".

Usage Examples

./fs-ro --ignore /proc --ignore /sys/fs

Output:

Everything is ok. 21 mount points checked.

Output (with read-only mount):

1 read-only mount point found: /dev/sda1 on / (type ext4)

States

  • OK if no unexpected read-only mount points are found.

  • WARN if one or more mount points (not on the ignore list) are mounted read-only.

  • --always-ok suppresses all alerts and always returns OK.

Perfdata / Metrics

There is no perfdata.

Credits, License