2

This will still write to /dev/foo if there is a journal:

mount -oro /dev/foo /mnt/disk

How can I treat /dev/foo as read-only?

  • The question may make sense to you, but you should explain the issue for others (including google). Such as "The ext4 journal is automatically replayed on mount, how can I prevent this, and all other writes to the underlying device". The title is also misleading, as the filesystem is read only. – Patrick Jan 15 '17 at 23:30
4
mount -oro,noload /dev/foo /mnt/disk
  • 4
    You should explain the answer, and what the option does. – Patrick Jan 15 '17 at 23:30
2

If you make the device readonly first:

blockdev --setro /dev/foo

then the filesystem will be unable to write to it, so you don't need to know any special type-dependent filesystem options.

  • blockdev is only able to block rw access from userspace. There still can be rw access to a device even if set ro using blockdev. See also lkml.org/lkml/2007/2/6/1 and other references online. – Gen.Stack Apr 15 at 13:34

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