I'm shredding files on large ext3 file systems (e.g. see this article for how I do this).
In order to achieve this I need to mount the ext3 file systems without journaling. To most of them I get by with just unmounting them and re-mounting them as ext2. But some file systems can't be unmounted (e.g. /) and attempts to use "-o remount,data=writeback" fails with errors.
Is it possible to turn off journaling of a mounted ext3 file system without having to unmount it?
Best Answer
To the best of my knowledge you cannot change file system mount parameters without re-mounting it.
By the way, the article you refer to cites shred man page, which says: "In the case of ext3 file systems, the above disclaimer applies (and shred is thus of limited effectiveness) only in data=journal mode, which journals file data in addition to just metadata. In both the data=ordered (default) and data=writeback modes, shred works as usual."
Have a look at (or post) your /etc/fstab. Chances are you don't need to change journaling mode on the filesystem.