Hi, I see a strange behaviour when playing with the metadata_csum parameter of ext4. (I use a Debian Stretch, with a kernel 4.9.0-8-amd64 #1 SMP Debian 4.9.110-3+deb9u6 (2018-10-08) x86_64 GNU/Linux) How to reproduce : * I enable metada checksum : OK root@test# tune2fs -O metadata_csum /dev/my_vol tune2fs 1.43.4 (31-Jan-2017) Enabling checksums could take some time. Proceed anyway (or wait 5 seconds) ? (y,N) y * I check : Checksum enabled root@test# tune2fs -l /dev/my_vol tune2fs 1.43.4 (31-Jan-2017) Filesystem volume name: <none> [...] Journal backup: inode blocks Checksum type: crc32c Checksum: 0xb0e3a180 * I change filesystem UUID : OK root@test# tune2fs -U random /dev/my_vol tune2fs 1.43.4 (31-Jan-2017) Setting UUID on a checksummed filesystem could take some time. Proceed anyway (or wait 5 seconds) ? (y,N) y * I disable metadata checksum : OK root@test# tune2fs -O ^metadata_csum /dev/my_vol tune2fs 1.43.4 (31-Jan-2017) Disabling checksums could take some time. Proceed anyway (or wait 5 seconds) ? (y,N) y * I change filesystem UUID : It looks like metada checksum still is enabled root@test# tune2fs -U random /dev/my_vol tune2fs 1.43.4 (31-Jan-2017) Setting UUID on a checksummed filesystem could take some time. Proceed anyway (or wait 5 seconds) ? (y,N) y * I fsck the filesystem to see if it could fix this. root@test# e2fsck -f /dev/my_vol 2fsck 1.43.4 (31-Jan-2017) Pass 1: Checking inodes, blocks, and sizes Pass 2: Checking directory structure Pass 3: Checking directory connectivity Pass 4: Checking reference counts Pass 5: Checking group summary information /dev/my_vol: 16303/3932160 files (0.9% non-contiguous), 1829950/15728640 blocks * I check : metadata checksum looks like disabled root@test# tune2fs -l /dev/my_vol tune2fs 1.43.4 (31-Jan-2017) Filesystem volume name: <none> [...] Journal backup: inode blocks * I change filesystem UUID : It looks like metada checksum still is enabled root@test# tune2fs -U random /dev/my_vol tune2fs 1.43.4 (31-Jan-2017) Setting UUID on a checksummed filesystem could take some time. Proceed anyway (or wait 5 seconds) ? (y,N) y Is it a bug ? How can I actually disable this parameter ? Best regards, jC Guillain -- IMPORTANT NOTICE: The contents of this email and any attachments are confidential and may also be privileged. If you are not the intended recipient, please notify the sender immediately and do not disclose the contents to any other person, use it for any purpose, or store or copy the information in any medium. Thank you.