One of the neat features that zfs allows you to implement is to create a zfs filesystem out of a file. It’s especially useful when you need to create a secure or portable filesystem.

Usually I use this method in order to create a small secure zfs volume that I may move to another system in the future by simply copying the files that represent a zfs filesystem.

Creating a pool

I prefer to create a separate directory for pool files:

  • mkdir zfs-pool-something

Then you need to create a file. There are two ways you can do so:

  • truncate -s 256M zfs-pool-something-1
  • dd if=/dev/zero of=zfs-pool-something-1 bs=1M count=256

Where 256M and bs=1M count=256 are equal to 256 megabytes.

And finally, create a pool:

  • sudo zpool create -o ashift=12 -f zfs-pool-something /path/zfs-pool-something-1

Importing a pool

To import the pool you ned to specify its name and its path:

  • sudo zpool import -d /path/zfs-pool-something zfs-pool-something

Exporting a pool

The idea is the same as for any other zfs pool:

  • sudo zpool export zfs-pool-something

Expanding a pool

In order to expand a pool you have at least 2 ways:

  1. Create a new file and add it to the pool.
  2. Create a new file and replace the old file with the new one.

Adding a new file to the pool

This it the method I usually use.

To accomplish this you need to:

  1. Create a new file:
    • truncate -s 512M zfs-pool-something-2
  2. Add the file to the pool:
    • sudo zpool add zfs-pool-something /path/zfs-pool-something-2

Replacing an old file with a new one

To increase a zfs pool size by replacing an old file with a new one you need to:

  1. Create a new file:
    • truncate -s 512M zfs-pool-something-2
  2. Replace the old file:
    • sudo zpool replace zfs-pool-something /path/zfs-pool-something/zfs-pool-something-1 /path/zfs-pool-something/zfs-pool-something-2

Creating a pool with secure dataset

To accomplish this goal you need to:

  1. Create a new file:
    • truncate -s 256M zfs-pool-something-1
    • dd if=/dev/zero of=zfs-pool-something-1 bs=1M count=256
  2. Create a pool:
    • sudo zpool create -o ashift=12 -f zfs-pool-something /path/zfs-pool-something-1
  3. Create an encrypted dataset:
    • sudo zfs create -o encryption=on -o keyformat=passphrase zfs-pool-something/encrypted-dataset
Author: Savelii Pototskii
Date:
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Copyright: CC-BY
Categories: linux