Hi everyone, I’m back again with another perl script to hopefully be useful to a few of you.

Firstly, the script: http://lee.hinmanphoto.com/files/zdiff.txt (formatting long scripts in wordpress’ crazy editor is a very long and arduous process, thus I’m just linking to the script in this case, if anyone knows of a better place to stick it let me know). chmod +x it and away you go!

Edit: Sun was nice enough to host the file for me, here’s a link to their version in case the other one goes down: http://www.sun.com/bigadmin/scripts/submittedScripts/zdiff.txt

In a nutshell, here’s what it does:

• Allows you to diff a file inside a ZFS snapshot with the current file in the filesystem and (optionally) print out the line differences
• Recursively diff an entire snapshot using md5 sums and (optionally) printing out the line differences
• Display the md5 sums for each file in a ZFS snapshot and filesystem (this can get old to look at very quickly)

Basically, that doesn’t mean a whole lot, here’s the output from the -h option:

ZFS Snapshot diff
./zdiff.pl [-dhirv] <zfs shapshot name> [filename]

-d Display the lines that are different (diff output)
-h Display this usage
-i Ignore files that don't exist in the snapshot (only necessary for recursing)
-r Recursively diff every file in the snapshot (filename not required)
-v Verbose mode

[filename] is the filename RELATIVE to the ZFS snapshot root. For example, if
I had a filesystem snapshot called pool/data/zone@initial. The filename '/etc/passwd'
would refer to the filename /pool/data/zone/etc/passwd in the filesystem and filename
/pool/data/zone/.zfs/snapshot/initial/etc/passwd in the snapshot.

A couple of examples:
./zdiff.pl -v -r -i pool/zones/lava2019@Fri
Checks the current pool/zones/lava2019 filesystem against the snapshot
returning the md5sum difference of any files (ignore files that don't
exist in the snapshot). With verbose mode

./zdiff.pl -d pool/zones/lava2019@Mon /root/etc/passwd
Check the md5sum for /pool/zones/lava2019/root/etc/passwd and compare
it to /pool/zones/lava2019/.zfs/snapshot/Mon/root/etc/passwd. Display
the lines that are different also.

Here’s what the output is going to look like:

-bash-3.00# ./zdiff.pl -d -v -r -i pool/zones/lava2019@Fri
Recursive diff on pool/zones/lava2019@Fri
Filesystem: /pool/zones/lava2019, Snapshot: Fri
Comparing: /pool/zones/lava2019/
to: /pool/zones/lava2019/.zfs/snapshot/Fri/
** /pool/zones/lava2019/root/etc/shadow is different
** MD5(/pool/zones/lava2019/root/etc/shadow)= 04fa68e7f9dbc0afbf8950bbb84650a6
** MD5(/pool/zones/lava2019/.zfs/snapshot/Fri/root/etc/shadow)= 4fc845ff7729e804806d8129852fa494
17d16
< tom:*LK*:::::::
** /pool/zones/lava2019/root/etc/dfs/dfstab is different
** MD5(/pool/zones/lava2019/root/etc/dfs/dfstab)= 8426d34aa7aae5a512a0c576ca2977b7
** MD5(/pool/zones/lava2019/.zfs/snapshot/Fri/root/etc/dfs/dfstab)= c3803f151cb3018f77f42226f699ee1b
13d12
< share -F nfs -o rw -d "Data" /data

etc, etc, etc.

I am planning on using it so I can audit certain files on different zones (like /etc/passwd) against an initial ZFS snapshot to see what’s changed. Nice little way to keep track of stuff. Email me with any bugs. Matthew dot hinman at gmail dot com.