[CentOS] KVM on CentOS 6

[Emmett Culley]

On 09/08/2011 02:25 AM, Nick wrote:
> On 08/09/11 07:23, Emmett Culley wrote:
>> Today I suddenly have two VMs that have read only file systems.  The host is
>> CentOS 6, as are the two VMs with this problem.
> 
> Disclaimer: I can't claim this matches your circumstance exactly, but it is
> something you might check.
> 
> I have seen problems with LVM partitions in KVM guests being unwritable, despite
> being mounted read-write, on CentOS5.6 (host and guest). Specifically, I was
> booting a guest from the CentOS live CD in order to fix /etc/fstab on the root
> partition, which was LVM, but I could not save my changes.
> 
> Executing 'vgscan' resolved my problem; I'm not clear exactly why, but I could
> then remount and write successfully.  You might also try 'vgchange -ay' if that
> doesn't work.
> 
> Perhaps:
>   - boot with liveCD .iso in a virtual CD drive
>   - check whether VolGroup-lv_root is mounted and writeable
>     (use mount, lvdisplay, touch etc.)
>   - if not, unmount it, run vgscan
>   - remount it, and check for writability again
> 
> N
I will give that a try.  However I remembered something about both failed VMs from my investigations yesterday and checked it out this morning on the one that is still available.  The last lines of syslog (/var/log/messages) are:

Sep  6 19:42:49 dev squid[2885]: Ready to serve requests.
Sep  6 19:42:50 dev squid[2885]: storeLateRelease: released 0 objects
Sep  7 00:16:55 dev fail2ban.actions: WARNING [apache-pma] Ban 82.165.150.194
Sep  7 15:47:06 dev mountd[1658]: authenticated unmount request from 192.168.6.12:603 for /web (/web)
Sep  7 15:49:33 dev mountd[1658]: authenticated mount request from 192.168.6.12:699 for /web (/web)
Sep  7 15:49:34 dev mountd[1658]: authenticated mount request from 192.168.6.12:863 for /web (/web)
Sep  7 21:19:59 dev init: tty (/dev/tty1) main process ended, respawning
Sep  7 21:59:23 dev kernel: ata1.00: exception Emask 0x0 SAct 0x0 SErr 0x0 action 0x6 frozen
Sep  7 21:59:23 dev kernel: ata1.00: failed command: WRITE DMA
Sep  7 21:59:23 dev kernel: ata1.00: cmd ca/00:08:a0:02:31/00:00:00:00:00/e3 tag 0 dma 4096 out
Sep  7 21:59:23 dev kernel:         res 40/00:01:00:00:00/00:00:00:00:00/a0 Emask 0x4 (timeout)
Sep  7 21:59:23 dev kernel: ata1.00: status: { DRDY }
Sep  7 21:59:23 dev kernel: ata1: soft resetting link
Sep  7 21:59:23 dev kernel: ata1.00: configured for MWDMA2
Sep  7 21:59:23 dev kernel: ata1.00: device reported invalid CHS sector 0
Sep  7 21:59:23 dev kernel: ata1: EH complete

So it looks like there is a bug I can report.  But where to report it?  I don't see how it can be a CentOS 6 bug.

Emmett