[CentOS] CentOS on VPS File System in read-only mode

Sat Sep 13 22:15:01 UTC 2014
Greg Lindahl <lindahl at pbm.com>

On Sat, Sep 13, 2014 at 06:46:40PM -0300, Pablo Parodi wrote:

> Every saturday (I have installed this vps since 3 weeks ago) I check the
> status of the server I found that the file system is in read-only mode

The most common reason for this is a disk that is throwing errors. When this is
the system disk, it inhibits logging the error in /var/log/messages. However,
the error will be logged in other places.

3 places to check:

1) Run the 'dmesg' command, look for errors
1a) (If you had a remote syslog server configured, you won't miss errors
in /var/log/messages because the system disk is read-only)

2) 'cat /dev/vcs' to see if there is anything on the console. (A server will
ideally have a console log configured to not miss anything.)

3) 'smartctl -a /dev/sda' will show you if the disk has failed its self-test.
(Ideally you have it configured to email you in this case.)

> I suppose that the issue is a very high I/O request on the HD during the
> backup process.

I have never seen high I/O rates cause a read-only filesystem, except
in the case where a disk error was visible. Linux has no problems with
extremely busy disks; I have clusters with 100s of servers that run their
disks with high I/O requests 24 hours a day for years, with no problems that
were not visible in the logs 1-3.

-- greg

p.s. your English is pretty good!