How to create a XFS filesystem using a file

Sometimes we need to test on a XFS filesystem, just create a fake one using a file.

1.Create a 500MB temp file

# dd if=/dev/zero of=openkbtest count=999999
999999+0 records in
999999+0 records out
511999488 bytes (512 MB) copied, 0.89366 seconds, 573 MB/s

# ls -altr openkbtest
-rw-r--r-- 1 root root 511999488 Aug 16 14:31 openkbtest 

2.Format the file to XFS filesystem

# /sbin/mkfs -t xfs -q openkbtest

3.Create a directory which will be the mount point

$ mkdir testmount

4.Check loopback device number,most likely we can start with loop0 if it is not used by others.

$ cat /proc/mounts|grep loop
$ cd /dev
[dev]$ ls -altr|grep loop
brw-r-----  1 root disk   7,     0 Jun 14 15:04 loop0
brw-r-----  1 root disk   7,     1 Jun 14 15:04 loop1
brw-r-----  1 root disk   7,     2 Jun 14 15:04 loop2
brw-r-----  1 root disk   7,     3 Jun 14 15:04 loop3
brw-r-----  1 root disk   7,     4 Jun 14 15:04 loop4
brw-r-----  1 root disk   7,     5 Jun 14 15:04 loop5
brw-r-----  1 root disk   7,     6 Jun 14 15:04 loop6
brw-r-----  1 root disk   7,     7 Jun 14 15:04 loop7

5.Mount it

# mount -o loop=/dev/loop0 /data/tmp/openkbtest /data/xxx/testmount

# cat /proc/mounts|grep loop
/dev/loop0 /data/xxx/testmount xfs rw,noquota 0 0