CentOS On VPS File System In Read-only Mode

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Hello All,

First of all I want say thanks for all the info I see every time in this list. Second, sorry for my basic english.

I writting this because I’m experiencing an issue with a CentOS over a VPS. 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

#touch test touch: cannot touch `test’: Read-only file system

# mount -o remount /
mount: block device /dev/sda1 is write-protected, mounting read-only

Looking for info in the logs, I don’t know how to get the root cause of the issue. But I can see that the last writing process is marked about the 1:40

#ls -ltr – /var/log
-rw——- 1 root root 479825 Sep 13 01:20 maillog
-rw——- 1 root root 229268 Sep 13 01:30 cron
-rw——- 1 root root 106941 Sep 13 01:34 messages

(now is Sep 13 18hr)

The CentOS is mounted on a VPS. The VPS server is a Proxmox. The sysadmin of the VPS told me that there is a backup process running on friday at midnight.

I suppose that the issue is a very high I/O request on the HD during the backup process.
( example in vmware http://kb.vmware.com/selfservice/microsites/search.do?language=en_US&cmd=displayKC&externalIdQ306

# uname -a Linux 2.6.18-371.12.1.el5 #1 SMP Wed Sep 3 16:22:34 EDT 2014 x86_64 x86_64
x86_64 GNU/Linux

There is any kind of workarround for this (make the CentOS more flexible about the I/O timeouts or fails)
Or maybe there is something to recommend to the VPS sysadmin to solve this issue?

more info:
# more /etc/fstab LABEL=/ / ext3 defaults 1 1
tmpfs /dev/shm tmpfs defaults 0 0
devpts /dev/pts devpts gid=5,modeb0 0 0
sysfs /sys sysfs defaults 0 0
proc /proc proc defaults 0 0
LABEL=SWAP-sda2 swap swap defaults 0 0

#df -h Filesystem Size Used Avail Use% Mounted on
/dev/sda1 19G 3.4G 15G 19% /
tmpfs 502M 0 502M 0% /dev/shm

The previous times it happened the fsck after a reboot fixed the issue.

Thanks in advance. PP

One thought on - CentOS On VPS File System 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 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!