[libvirt-users] Questions and a blockpull issue

Abbas akhan at phi9.com
Mon Oct 22 19:18:43 UTC 2012

>> 3. Where is the virsh bash_completion conf.d file from upstream; since el6
>> rpm for it seems have tab completion built right into virsh shell.
> Sadly, we do not yet have a bash_completion file for virsh yet.  It's
> been on my back-burner of things that would be nice to write, if I ever
> had time, and I even think there have been some proposed patches, but
> none upstream yet.
Hm. I did find old bash_completion files here in mailing list archive. 
Gonna borrow from there.

> Also, what are you trying to pull? If you are starting with the chain: 
> co1.img <- co1.capture1 then pulling with a --base of co1.img is a 
> no-op (co1.img is ALREADY the backing file of co1.capture1); the only 
> other alternative is to pull without a --base argument, which moves 
> all of co1.img contents into co1.capture1 and leaves co1.capture1 
> without a backing image. Partial pull (where --base is specified) only 
> makes sense when you have a chain longer than 2 files. 

Thanks. That does make sense. I was trying to pull from the backing 
image but wanted to flat down snapshot image and backing image. Not 
specifying --base exactly does what I want.

Two more quick questions though.

1. "virsh blockcommit" would be opposite to blockpull, right? But sing 
it with latest stable kvm 1.2.0 tells that this feature is not yet 
supported. Is it still being developed?

2. I assume that there is no need to quiesce the image while creating a 
snapshot or after a blockpull since the pull function works at block 
level to avoid fs corruption. Please correct me if I am wrong. I am 
gonna be testing with a few kvm domains running database servers which 
usually are highly vulnerable to db corruption issues if image files are 
manhandled while data is being accessed.

>> [root at KVM libvirt]# virsh -d 0 blockpull --domain CO1 --path
>> /home/vms/co1.capture1  --base /home/vms/co1.img --verbose --wait
>> blockpull: domain(optdata): CO1
>> blockpull: path(optdata): /home/vms/co1.capture1
>> blockpull: base(optdata): /home/vms/co1.img
>> blockpull: verbose(bool): (none)
>> blockpull: wait(bool): (none)
>> blockpull: found option <domain>: CO1
>> blockpull: <domain> trying as domain NAME
>> Block Pull: [100 %]
>> Pull complete
> That is correct (no-op) usage.  What wikis are you referring to that led
> you to the assumption that this is reversed argument order?

The Fedora wiki currently shows the reverse argument order.



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