Show Table of Contents
14.5.15. Using blockcommit to Shorten a Backing Chain
This section demonstrates how to use
virsh blockcommit to shorten a backing chain. For more background on backing chains, see Section 14.5.18, “Disk Image Management with Live Block Copy”.
blockcommit copies data from one part of the chain down into a backing file, allowing you to pivot the rest of the chain in order to bypass the committed portions. For example, suppose this is the current state:
base ← snap1 ← snap2 ← active.
Using
blockcommit moves the contents of snap2 into snap1, allowing you to delete snap2 from the chain, making backups much quicker.
Procedure 14.2. virsh blockcommit
- Run the following command:
#
virsh blockcommit $dom $disk -base snap1 -top snap2 -wait -verboseThe contents of snap2 are moved into snap1, resulting in:base ← snap1 ← active. Snap2 is no longer valid and can be deletedWarning
blockcommitwill corrupt any file that depends on the-baseoption (other than files that depend on the-topoption, as those files now point to the base). To prevent this, do not commit changes into files shared by more than one guest. The-verboseoption allows the progress to be printed on the screen.
Where did the comment section go?
Red Hat's documentation publication system recently went through an upgrade to enable speedier, more mobile-friendly content. We decided to re-evaluate our commenting platform to ensure that it meets your expectations and serves as an optimal feedback mechanism. During this redesign, we invite your input on providing feedback on Red Hat documentation via the discussion platform.