Hi, For Btrfs and more recently XFS they explicitly support changing the label while mounted. Documentation is available saying it can be done and stracing shows it is using a file system specific ioctl() to make the change. However for ext2/3/4 file systems I can't find anything explicitly documented, and stracing "tune2fs -L" shows that it writes directly to the block device while the file system is mounted. That seems unsafe as I presume the kernel would be expecting to have exclusive access to the block device while the file system is mounted. However it always seems to work. I am wondering if it is safe and supported to change an ext2/3/4 file system label while it is mounted? (I have a old GParted enhancement request for this, hence the question. https://bugzilla.gnome.org/show_bug.cgi?id=600496) Thanks, Mike # mkfs.btrfs /dev/sdb1 # mount /dev/db1 /mnt/1 # strace btrfs filesystem label /mnt/1 btrfs_label ... open("/mnt/1", O_RDONLY|O_NOATIME) = 3 ioctl(3, BTRFS_IOC_SET_FSLABEL, "btrfs_label") = 0 # mkfs.xfs /dev/sdb2 # mount /dev/sdb2 /mnt/2 # strace xfs_io -c "label -s xfs_label" /mnt/2 ... open("/mnt/2", O_RDONLY) = 3 ... ioctl(3, BTRFS_IOC_SET_FSLABEL, "xfs_label") = 0 # mkfs.ext2 /dev/sdb3 # mount /dev/sdb3 /mnt/3 # strace tune2fs -L ext2_label /dev/sdb3 ... open("/dev/sdb3", O_RDWR) = 3 ... lseek(3, 134217728, SEEK_SET) = 134217728 write(3, "\0\200\0\0\0\0\2\0\231\31\0\0\217\367\1\0\365\177\0\0\0\0\0\0\2\0\0\0\2\0\0\0"..., 1024) = 1024 lseek(3, 402653184, SEEK_SET) = 402653184 write(3, "\0\200\0\0\0\0\2\0\231\31\0\0\217\367\1\0\365\177\0\0\0\0\0\0\2\0\0\0\2\0\0\0"..., 1024) = 1024 fsync(3) = 0 lseek(3, 1072, SEEK_SET) = 1072 write(3, "\vM", 2) = 2 lseek(3, 1144, SEEK_SET) = 1144 write(3, "ext2_label", 10) = 10 fsync(3) = 0 close(3)
