Explanation bug in mkfs xfs Filesystem mkfs from util-linux 2.26.2

[Stephan]

mkfs from util-linux 2.26.2

during an exercise with creating xfs partitions on a Ubuntu 15.10 64 Bit virtual machine,
I guess I found a bug.

Explanation:
When creating an xfs filesystem on a partition with a existing gpt table, the mkfs command return an error message
with the advice to force the command to run by using the -f option (lowercase f)

However, it wont work and as you can see at my bash text, the command tells me that -f (lowercase f) is an invalid option.
I read the manpages of mkfs to determine what should be the correct option. Even here, the -f (lowercase f) is mentioned.

  -f Force overwrite when an existing filesystem is detected on the device. By default, mkfs.xfs will not write to the device if it suspects that there is a filesystem or partition table on the device already.

So I tried the uppercase F (-F) to FORCE the command to overwrite everything which worked !
So there are 2 possibilities:
#1 I am to dump to use a -f properly
#2 The texts (man pages and stderr)are wrong written and should be replaced with a uppercase F.

root@ubuntu:/mnt# mkfs -t xfs /dev/sdb2
mkfs.xfs: /dev/sdb2 appears to contain a partition table (gpt).
mkfs.xfs: Use the -f option to force overwrite.
root@ubuntu:/mnt# mkfs -tf xfs /dev/sdb2
mkfs: failed to execute mkfs.f: No such file or directory
root@ubuntu:/mnt# mkfs -t -f xfs /dev/sdb2
mkfs: failed to execute mkfs.-f: No such file or directory
root@ubuntu:/mnt# mkfs -f -t xfs /dev/sdb2
mkfs.ext2: invalid option -- 'f'

root@ubuntu:/mnt# mkfs -F -t xfs /dev/sdb2
mke2fs 1.42.12 (29-Aug-2014)
Found a gpt partition table in /dev/sdb2

Your mke2fs.conf file does not define the xfs filesystem type.
Creating filesystem with 512000 1k blocks and 128016 inodes
Filesystem UUID: 216b73d3-d57e-49b4-a288-b1a0ac9a5ce6
Superblock backups stored on blocks:
    8193, 24577, 40961, 57345, 73729, 204801, 221185, 401409

Allocating group tables: done
Writing inode tables: done
Writing superblocks and filesystem accounting information: done

Please give a feedback if my observation is correct or wrong.

With best regards

Stephan H. Wenderlich

[Phillip Susi (psusi)]

Your confusion is due to the difference between mkfs and mkfs.xfs. The latter wants you to pass it the -f, but to the former, this is an invalid option. The -f must follow the -t xfs so that mkfs does not interpret it and only passes it to mkfs.xfs.