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Detecting read-only file system in Linux

list Jeremy Laidman
Wed, 11 Mar 2015 10:58:28 +1100
Message-Id: <user-b461e05d6fd9@xymon.invalid>

On 11 March 2015 at 00:44, Thomas Eckert <user-2a86d6cd6326@xymon.invalid> wrote:
Just for future reference as you already found your solution:

From looking at the util-linux package I understand that _if_ the
/proc-filesystem is mounted the information is used from there.
I don't think this is the case.  Running "strace" on the "mount" command
shows that it first looks at /etc/mtab, and if that exists, it doesn't look
at /proc/mounts.  Only if /etc/mtab doesn't exist, does mount look at
/proc/mounts.

So in a situation where the filesystem containing /etc is having problems
and goes read-only, /etc/mtab won't get updated because it's now read-only.

J