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I've been using btrfs since 2012, and while as of 2014, it's far from done, it's gone a long way in that time. I thought I'd post some tips and scripts from things I've learned through my own use and sharing with others, hence this page.
More generally, you'll find Btrfs documentation on the btrfs wiki.

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2014/05/19 Btrfs-diff Between Snapshots
π 2014-05-19 01:01 in Btrfs, Linux

Differences between two btrfs snapshots

When you have historical snapshots, it may be useful to know what changed between 2 snapshots.

The best way to do this long term is to modify "btrfs send" to compute changes between the snapshots and just output the filelist instead of a stream with data.

However, until then, there is a hack that shows you files that got added and removed between two snapshots. It's not bulletproof like btrfs send, but it can give you a quick mostly working diff between two snapshots (*it will not show renames or deletes*). See more caveats on this original serverfault post.

legolas:/mnt/btrfs_pool1# btrfs-diff usr_ro.20140513_05:00:01/ usr_ro.20140514_06:00:02/ share/doc/linux-image-3.15.0-rc5-amd64-i915-preempt-20140216s1/buildinfo.gz share/doc/linux-image-3.15.0-rc5-amd64-i915-preempt-20140216s1/Buildinfo.gz share/doc/linux-image-3.15.0-rc5-amd64-i915-preempt-20140216s1/changelog.Debian.gz share/doc/linux-image-3.15.0-rc5-amd64-i915-preempt-20140216s1/Changes.gz (...)

You can download my latest snapshot of btrfs-diff. Note that I am not the author, it was copied from this serverfault post.

#!/bin/bash

# Author: http://serverfault.com/users/96883/artfulrobot # License: Unknown # # This script will show most files that got modified or added. # Renames and deletions will not be shown. # Read limitations on: # http://serverfault.com/questions/399894/does-btrfs-have-an-efficient-way-to-compare-snapshots # # btrfs send is the best way to do this long term, but as of kernel # 3.14, btrfs send cannot just send a list of changed files without # scanning and sending all the changed data blocks along.

usage() { echo $@ >&2; echo "Usage: $0 <older-snapshot> <newer-snapshot>" >&2; exit 1; }

[ $# -eq 2 ] || usage "Incorrect invocation"; SNAPSHOT_OLD=$1; SNAPSHOT_NEW=$2;

[ -d $SNAPSHOT_OLD ] || usage "$SNAPSHOT_OLD does not exist"; [ -d $SNAPSHOT_NEW ] || usage "$SNAPSHOT_NEW does not exist";

OLD_TRANSID=`btrfs subvolume find-new "$SNAPSHOT_OLD" 9999999` OLD_TRANSID=${OLD_TRANSID#transid marker was } [ -n "$OLD_TRANSID" -a "$OLD_TRANSID" -gt 0 ] || usage "Failed to find generation for $SNAPSHOT_NEW"

btrfs subvolume find-new "$SNAPSHOT_NEW" $OLD_TRANSID | sed '$d' | cut -f17- -d' ' | sort | uniq


More pages: March 2014 April 2014 May 2014 October 2014 March 2018

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