How do you compare two root filesystems - but ignore mount points?

Question

I have rootfs / but within that I have /mnt/another_rootfs which contains a second mounted rootfs.

I want to compare the files in them... but when I do somthng like: diff -r / /mnt/another_rootfs I start to get all the mount points being compared (which I am not so interested in) but also the / rootfs will also contain the second mounted /mnt/another_rootfs ... that is causing issues as well.

So I really just want to diff the files that are actually mounted on / vs the files mounted on /mnt/another_rootfs and not recurse into other mounts.

Is that possible?

I can recommend to use FreeFileSync - see this answer for screenshot in conjunction with Meld. — N0rbert, Oct 01 '18 at 16:33
@N0rbert I don't see how (in the answer) this gets around the mount point issue? — code_fodder, Oct 01 '18 at 16:37
You can set ignore filters in FFS if you want. Also you can ignore or include symlinks. — N0rbert, Oct 01 '18 at 16:38
ah... ok. Its a bit manual though for me. There are many mount points : (... but I suppose it could be done - thanks : ) — code_fodder, Oct 01 '18 at 16:41
Probably most easy way is to mount both /-filesystems under it's own mount-points in a live-session and compare the mount-points. — mook765, Oct 01 '18 at 17:56

waltinator · Answer 1 · 2018-10-01T23:37:22.060

1

A command line solution is easy, when you reverse the question to "I want to diff /mnt/another_rootfs /":

find /mnt/another_rootfs -xdev -type f -print0 | \
    xargs -0 -r $HOME/bin/diffwithslash

Where $HOME/bin/diffwithslash is something like:

#!/bin/bash
while [[ $# -gt 0 ]] ; do
   afile="$1"
   shift
   bfile="${afile#/mnt/another_rootfs}"
   if [[ -f "$afile" ]] && [[ -f "$bfile" ]] ; then
       diff "$bfile" "$afile"
   fi
done
exit 0

edited Oct 01 '18 at 23:37

answered Oct 01 '18 at 16:55

waltinator

36,399

This would work : ) - but its more a script solution, I didn't really want to write a script if I could avoid it :o – code_fodder Oct 02 '18 at 08:08

score 1 · Answer 2 · answered Oct 02 '18 at 05:32

1

You can mount the partition which holds the /-file-system of the currently booted installation to a second mount-point and compare this mount-point with the mount-point of the other /-file-system.

Use lsblk -f to check which partition is mounted at /.

Then mount the partition with

sudo mount -t ext4 /dev/sdXY /mnt (replace XY with the found value)

Compare /mnt with the the folder which is the mount-point of the other /-file-system.

Unmount with sudo umount /mnt

answered Oct 02 '18 at 05:32

mook765

15,925

That helps - but the sub-mount points will still be there (like /proc and /sys etc...) is there a way to not recurse into these? – code_fodder Oct 02 '18 at 08:07
The mount-points /proc and /sys are empty folders on the disk. They are only populated in a running system. E.g the procfs provided by the kernel will be mounted to /proc. – mook765 Oct 02 '18 at 08:29

How do you compare two root filesystems - but ignore mount points?

2 Answers2