On Mon, 2026-03-02 at 12:07 +0100, Philipp Ludwig wrote:
> Am 2026-03-02 11:53, schrieb Dale:
> > Howdy,
> >
> > I did my weekly backups overnight. I had a lot of new files. I
> > was
> > wondering tho, can I generate a checksum or something for the
> > directory on my main rig and then generate it for my backup copy
> > and
> > then compare the two checksum results?
>
> You can use `find` to generate a checksum for every file:
>
> find /path/to/dir -type f -exec md5sum {} \; > output.md5
>
> Then, you transfer the output file to the new machine and run md5sum
> -c:
>
> md5sum --check < output.md5
>
> Beware that the path needs to match. So you may need to adjust the
> first parameter of `find` or play around with `sed` a bit.
>
> For example, I use this to verify the backup of my ~ folder. First,
> I go to /home/philipp and run
>
> find home/philipp/ -type f -exec md5sum {} \; > /tmp/home.md5
>
> Then, I go to the folder where I did the test restore, and verify:
>
> $ cd /mnt/data/backup-test-restore
> $ ls
> home
> $ cd home
> $ md5sum -c /tmp/home.md5
>
And for a quick user check (OK or not-OK), you can checksum the file
with checksums and compare its checksum on the other side.
Just do not forget that find does not sot the data in any user useful
way.
So I suggest sorting the checksum file first:
find home/philipp/ -type f -exec md5sum {} \; | sort> /tmp/home.md5
md5sum /tmp/home.md5S. > > While at it, how long would it take to do a directory that is about > > 42TBs in size? If it would take a long time to do it that way, is > > there a faster way to make sure the files match in a fairly quick > > way? > > It depends on the checksum algorithm. In the example above I used > md5, > which is considered deprecated, but fairly fast. Other examples would > be > sha256sum, sha512sum, etc. > > > Also, I use rsync to copy the files to the NAS box. Maybe it can > > do > > some sort of check while copying the files over??? > > rsync has a --checksum flag for this. > Also, you may want to look at rclone, which is a bit more > sophisticated > for > use cases like this: > > https://rclone.org/commands/rclone_sync/ > > HTH
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