[GH-ISSUE #10] Trouble on Cloudlinux VPS KVM istance #7

New issue

Closed

opened 2026-02-26 17:43:54 +03:00 by kerem · 3 comments

kerem commented

2026-02-26 17:43:54 +03:00

Owner

Originally created by @plant75 on GitHub (Jan 23, 2019).
Original GitHub issue: https://github.com/Corsinvest/cv4pve-autosnap/issues/10

Using eve4 to snap a Cloudlinux istance, the freeze option
cause filesystem lock.. it becomes read only.
We have tested it on 8 Server ( ZFS Filesystem )
The Web interface snap or replication snap are safe.
My question is, why do you use "freeze" ?
Is it possible to disable it and perform a standard zfs snapshot ?

Versione Italina:
Ciao Ragazzi, sempre molte grazie per il vostro tool veramente utilissimo.
Lo stiamo testando su 8 nodi Proxmox 5 (ZFS) ultima versione ma sulle istanze Cloudlinux ci causa un problema al kernel, che va in Read Only.
Gli snapshot fatti a riga di comando, via interfaccia web o quelli eseguiti dalle repliche sono OK.
Abbiamo notato che eve usa un opzione di freeze del Filesystem del VPS... e sembra questa la causa.
Forse è usato per renderlo compatibile con LVM ?.. sarebbe possibile poterlo disabilitare ?

Grazie!

Originally created by @plant75 on GitHub (Jan 23, 2019). Original GitHub issue: https://github.com/Corsinvest/cv4pve-autosnap/issues/10 Using eve4 to snap a Cloudlinux istance, the freeze option cause filesystem lock.. it becomes read only. We have tested it on 8 Server ( ZFS Filesystem ) The Web interface snap or replication snap are safe. My question is, why do you use "freeze" ? Is it possible to disable it and perform a standard zfs snapshot ? ---------------------------------------------------------------------------- Versione Italina: Ciao Ragazzi, sempre molte grazie per il vostro tool veramente utilissimo. Lo stiamo testando su 8 nodi Proxmox 5 (ZFS) ultima versione ma sulle istanze Cloudlinux ci causa un problema al kernel, che va in Read Only. Gli snapshot fatti a riga di comando, via interfaccia web o quelli eseguiti dalle repliche sono OK. Abbiamo notato che eve usa un opzione di freeze del Filesystem del VPS... e sembra questa la causa. Forse è usato per renderlo compatibile con LVM ?.. sarebbe possibile poterlo disabilitare ? Grazie!

kerem closed this issue

2026-02-26 17:43:54 +03:00

kerem commented

2026-02-26 17:43:55 +03:00

Author

Owner

@plant75 commented on GitHub (Jan 23, 2019):

Cloudlinux response:
Our devs have checked the dump, and the situation is next:

The issue is not related to CloudLinux directly, but to Qemu agent, which does not freeze the file system(s) correctly. What is actually happening:

When VM backup is invoked, Qemu agent freezes the file systems, so no single change will be made during the backup. But Qemu agent does not respect the loop* devices in freezing order (we have checked its sources), which leads to the next situation:

freeze loopback fs
---> send async reqs to loopback thread
freeze main fs
loopback thread wakes up and trying to write data to the main fs, which is still frozen, and this finally leads to the hung task and kernel crash.

You can check your other VMs, I believe there will be no such mounts:

/dev/loop0 /tmp ext3 rw,nosuid,noexec,relatime,data=ordered 0 0
/dev/loop0 /var/tmp ext3 rw,nosuid,noexec,relatime,data=ordered 0 0

@plant75 commented on GitHub (Jan 23, 2019): Cloudlinux response: Our devs have checked the dump, and the situation is next: The issue is not related to CloudLinux directly, but to Qemu agent, which does not freeze the file system(s) correctly. What is actually happening: When VM backup is invoked, Qemu agent freezes the file systems, so no single change will be made during the backup. But Qemu agent does not respect the loop* devices in freezing order (we have checked its sources), which leads to the next situation: 1) freeze loopback fs ---> send async reqs to loopback thread 2) freeze main fs 3) loopback thread wakes up and trying to write data to the main fs, which is still frozen, and this finally leads to the hung task and kernel crash. You can check your other VMs, I believe there will be no such mounts: /dev/loop0 /tmp ext3 rw,nosuid,noexec,relatime,data=ordered 0 0 /dev/loop0 /var/tmp ext3 rw,nosuid,noexec,relatime,data=ordered 0 0

kerem commented

2026-02-26 17:43:55 +03:00

Author

Owner

@franklupo commented on GitHub (Jan 24, 2019):

Hi,
new version in test. New version is a client to connect via API.

@franklupo commented on GitHub (Jan 24, 2019): Hi, new version in test. New version is a client to connect via API.

kerem commented

2026-02-26 17:43:55 +03:00

Author

Owner

@franklupo commented on GitHub (Jan 24, 2019):

Using eve4 to snap a Cloudlinux istance, the freeze option
cause filesystem lock.. it becomes read only.
We have tested it on 8 Server ( ZFS Filesystem )
The Web interface snap or replication snap are safe.
My question is, why do you use "freeze" ?
Is it possible to disable it and perform a standard zfs snapshot ?

Versione Italina:
Ciao Ragazzi, sempre molte grazie per il vostro tool veramente utilissimo.
Lo stiamo testando su 8 nodi Proxmox 5 (ZFS) ultima versione ma sulle istanze Cloudlinux ci causa un problema al kernel, che va in Read Only.
Gli snapshot fatti a riga di comando, via interfaccia web o quelli eseguiti dalle repliche sono OK.
Abbiamo notato che eve usa un opzione di freeze del Filesystem del VPS... e sembra questa la causa.
Forse è usato per renderlo compatibile con LVM ?.. sarebbe possibile poterlo disabilitare ?

Grazie!

The command used are "qm vmid snapshot" no parameter freeze. If you install tools in guest the proxmox execute operation. What is the command that uses for snapshot?

Best regards

@franklupo commented on GitHub (Jan 24, 2019): > Using eve4 to snap a Cloudlinux istance, the freeze option > cause filesystem lock.. it becomes read only. > We have tested it on 8 Server ( ZFS Filesystem ) > The Web interface snap or replication snap are safe. > My question is, why do you use "freeze" ? > Is it possible to disable it and perform a standard zfs snapshot ? > > Versione Italina: > Ciao Ragazzi, sempre molte grazie per il vostro tool veramente utilissimo. > Lo stiamo testando su 8 nodi Proxmox 5 (ZFS) ultima versione ma sulle istanze Cloudlinux ci causa un problema al kernel, che va in Read Only. > Gli snapshot fatti a riga di comando, via interfaccia web o quelli eseguiti dalle repliche sono OK. > Abbiamo notato che eve usa un opzione di freeze del Filesystem del VPS... e sembra questa la causa. > Forse è usato per renderlo compatibile con LVM ?.. sarebbe possibile poterlo disabilitare ? > > Grazie! The command used are "qm vmid snapshot" no parameter freeze. If you install tools in guest the proxmox execute operation. What is the command that uses for snapshot? Best regards