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Re: [rdiff-backup-users] Re: rdiff-backup --verify 1.2.8 running around

From: Dominic Raferd
Subject: Re: [rdiff-backup-users] Re: rdiff-backup --verify 1.2.8 running around in circles
Date: Mon, 21 Feb 2011 06:06:15 +0000
User-agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv: Gecko/20101208 Thunderbird/3.1.7

On 21/02/11 00:22, Robert Nichols wrote:
On 02/20/2011 02:51 PM, Marc Haber wrote:
On Sun, Feb 20, 2011 at 06:11:19PM +0000, Dominic Raferd wrote:
Secondly, rdiff-backup --verify switch gives only a partial verification
of the repository. Daniel Miller wrote a patch, available for
rdiff-backup 1.2.8, which adds --verify-full and --verify-full-at-time
switches which can perform a full verification of a repository.

Debian's version does not seem to be patched. What does --verify omit?

--verify only checks the latest version of data in the repository, and because rdiff-backup works with reverse diffs this is far from confirming that the entire repository is okay. --verify-at-time allows you to check earlier date, but even checking a very early date (e.g. before the first backup) does not guarantee integrity of subsequent backups e.g. for files that did not exist at the earlier time. Without the patch, the only safe way is to run --verify-at-time for every time a backup set has been updated in the repository, but this is often impractical.

If you read the last message from Dan Miller in that "New feature:
--verify-full" thread you see why versions including that patch have not
been distributed.


Yes. This version cannot for instance create new repositories. Daniel had backported it from his original patch (for rdiff-backup in CSV), and there are some glitches. So I only use it for the --verify-full and --verify-full-at-time options - I build but don't install it. For all other purposes I use standard rdiff-backup 1.2.8.

And, it wouldn't help for your case anyway.  The patch file contains the

+WARNING this will not detect if your repository has already been corrupted. +It will create integrity signatures with the files as they exist when you +run the script. Any corruption that happened before that point can only +be detected with --verify-at-time. However, after you run this script you +can use --verify-full to verify that nothing has changed since you ran this

I think this warning refers to the integrify.py module not to the patch as a whole. The comment for the whole patch is:

+Added --verify-full, which verifies the integrity of an entire repository
+including all increments and metadata. This should be much faster than
+--verify-at-time=<date in the past>, and is more comprehensive in terms of
+what is verified.

The "--verify" and "--verify-at-time now" options are OK for checking the
current mirror (aside from problems with files having multiple hard links, which rdiff-backup stumbles with in other places too). The big problem is not having a way to verify the entire archive. The suggestion on the wiki site to pick a date that is at least as old as the oldest rdiff session is
very wrong.  Only the content that existed on that oldest date will be
checked. Many forms of corruption for subsequent dates will go unnoticed.

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