How to use a file as a zpool?

Question

If I do

dd if=/dev/zero of=/tank/test/zpool bs=1M count=100

how can I treat the file /tank/test/zpool as a vdev, so I can use it as a zpool?

It is for zfs testing purposes only.

maybe you are missing a needed information, you are using solaris or linux? — c4f4t0r, Mar 21 '14 at 18:42

score 26 · Accepted Answer · answered Mar 21 '14 at 19:38

26

There is no need to create a loop device, you can simply use the file itself as a vdev:

zpool create test /tank/test/zpool

answered Mar 21 '14 at 19:38

jlliagre

3

This is correct. – ewwhite Mar 21 '14 at 19:46
1

sudo truncate -s 64M /tank/test/zpool – Max Robbertze Sep 17 '21 at 13:28
@MaxRobbertze That's indeed a way to create a file but the OP already created a 100M file with the alternate `dd` method. Moreover, `truncate` was probably unavailable on her 2014 Solaris version. – jlliagre Sep 17 '21 at 21:08

Mark Wagner · Answer 2 · 2014-03-21T18:22:03.960

5

Create a loop device backed by the file.

dd if=/dev/zero of=/tmp/foo bs=1M count=128
losetup /dev/loop0 /tmp/foo
zpool create tank /dev/loop0

(The minimum disk size of 128 MB.)

Oops, didn't notice the Solaris tag. My instructions were for Linux. Instead of losetup you can use lofiadm under Solaris.

edited Mar 21 '14 at 18:22

answered Mar 21 '14 at 18:10

Mark Wagner

The two last steps should be exchangeable as long as you don't instruct `losetup` to mount starting at a given offset. I.e. as long as you use the full file as the block device. – 0xC0000022L Nov 05 '18 at 09:44
Can this be used to bypass the "Cannot resolve path" error I get if the file is on a network filesystem instead of local? – Michael Jul 23 '20 at 20:40

2 Answers2