mount device and md5sum is changed

Asked Nov 05 '21 at 09:02

Active Nov 05 '21 at 10:18

Viewed 229 times

If mount sdc2 partition using mount -t ext4 -o ro /dev/sdc2 /mnt/bob2 then try to write file tihi 1.txt with command (of course unsuccessfully):

touch /mnt/bob2/ tihi 1.txt

When I do md5sum /dev/sdc2/, I get a different md5 hash (changed) than before, although my partition is read-only, I don't know why.

edited Nov 05 '21 at 10:18

AdminBee

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asked Nov 05 '21 at 09:02

John Stockton

if it works with `mount -o loop,ro` it's because ext4 writes even in ro mode – frostschutz Nov 05 '21 at 09:32
md5sum on a directory generally does not work (can work with recursive mode). Double check your commands and arguments to those commands. `touch /mnt/bob2 tihi 1.txt` affects **three** paths, not one. So add some quotes. Also include the md5sum checksum which is different between runs. – Ярослав Рахматуллин Nov 05 '21 at 10:18
@frostschutz What are you talking about? – Ярослав Рахматуллин Nov 05 '21 at 10:21
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https://unix.stackexchange.com/a/96508/30851 " the system may still write to the device " – frostschutz Nov 05 '21 at 10:35
Is `/dev/sdc2/` a typo? The trailing slash makes no sense. – Kamil Maciorowski Nov 05 '21 at 10:36
@ЯрославРахматуллин "Also include the md5sum checksum which is different between runs" why? you can't tell what changed – Bravo Nov 05 '21 at 10:48
@Bravo because I want to know that the author of the question is interpreting the data correctly. – Ярослав Рахматуллин Nov 05 '21 at 10:51
at a guess, I'd say since the ext4 filesystem superblock includes a `Mount time, in seconds since the epoch.` - the act of mounting it would, by definition, update that – Bravo Nov 05 '21 at 10:51
@ЯрославРахматуллин - seeing md5sum has changed doesn't take 4 years of computing science :p - OP states it's different and has changed - what more is there to say – Bravo Nov 05 '21 at 10:51
@Bravo neither does invoking a command on a single file with spaces, correctly. – Ярослав Рахматуллин Nov 05 '21 at 10:52
@ЯрославРахматуллин - true - also the `md5sum` command as shown wouldn't even run - guess the whole question is impossible – Bravo Nov 05 '21 at 10:56

mount device and md5sum is changed

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