Re: guest-fsfreeze-freeze freezes all mounted block devices
On Mon, Feb 17, 2020 at 10:03:27 +0100, Marc Roos wrote:
Hi Peter,
Should I assume that the virsh domfsfreeze, does not require the
qemu-agent service in the guest?
No. That's the official way how to drive the "guest-fsfreeze-freeze"
agent command via libvirt, thus you must have the guest agent the same
way as you used it before.
Using qemu-agent-command is a backdoor for testing arbitrary commands
and thus you can break things. You are on your own if stuff breaks using
that approach.
PS. I couldn't find the result. Afaik it looks like it is
returning the
amount of frozen/thawed filesystem's
qemu.git/gqa/qapi-schema.json says:
##
# @guest-fsfreeze-freeze:
#
# Sync and freeze all freezable, local guest filesystems. If this
# command succeeded, you may call @guest-fsfreeze-thaw later to
# unfreeze.
#
# Note: On Windows, the command is implemented with the help of a
# Volume Shadow-copy Service DLL helper. The frozen state is limited
# for up to 10 seconds by VSS.
#
# Returns: Number of file systems currently frozen. On error, all filesystems
# will be thawed. If no filesystems are frozen as a result of this call,
# then @guest-fsfreeze-status will remain "thawed" and calling
# @guest-fsfreeze-thaw is not necessary.
#
# Since: 0.15.0
You might also want to have a look at 'guest-fsfreeze-freeze-list'.
-----Original Message-----
Cc: libvirt-users
Subject: Re: guest-fsfreeze-freeze freezes all mounted block devices
On Fri, Feb 14, 2020 at 22:14:55 +0100, Marc Roos wrote:
>
> I wondered if anyone here can confirm that
>
> virsh qemu-agent-command domain
'{"execute":"guest-fsfreeze-freeze"}'
Note that libvirt implements this directly via 'virsh domfsfreeze'. This
is the corresponding man page entry:
domfsfreeze domain [[--mountpoint] mountpoint...]
Freeze mounted filesystems within a running domain to prepare for
consistent snapshots.
The --mountpoint option takes a parameter mountpoint, which is a
mount point path of the filesystem to be frozen.
This option can occur multiple times. If this is not specified,
every mounted filesystem is frozen.
> Freezes all mounted block devices filesystems. So if I use 4 block
> devices they are all frozen for snapshotting. Or just the root fs?
As a side note. For snapshotting via virsh snapshot-create use the
--quiesce option which does what you want or the virsh command with
arguments if you don't want to freeze everything.
Since you are using agent passthrough where libvirt doesn't do any
interpretation of what happens please refer to the appropriate QEMU
agent documentation for the semantics of the command you've used.