## ZFS

### Update / Upgrade

```bash
sudo apt update && sudo apt upgrade -y
```

### Enable the contrib repository

```bash
sudo nano /etc/apt/sources.list
```

```bash
#deb cdrom:[Debian GNU/Linux 13.3.0 _Trixie_ - Official amd64 NETINST with firmware 20260110-10:59]/ trixie contrib main non-free-firmware

deb http://deb.debian.org/debian/ trixie main contrib non-free-firmware
deb-src http://deb.debian.org/debian/ trixie main contrib non-free-firmware

deb http://security.debian.org/debian-security trixie-security main contrib non-free-firmware
deb-src http://security.debian.org/debian-security trixie-security main contrib non-free-firmware

# trixie-updates, to get updates before a point release is made;
# see https://www.debian.org/doc/manuals/debian-reference/ch02.en.html#_updates_and_backports
deb http://deb.debian.org/debian/ trixie-updates main contrib non-free-firmware
deb-src http://deb.debian.org/debian/ trixie-updates main contrib non-free-firmware

# This system was installed using removable media other than
# CD/DVD/BD (e.g. USB stick, SD card, ISO image file).
# The matching "deb cdrom" entries were disabled at the end
# of the installation process.
# For information about how to configure apt package sources,
# see the sources.list(5) manual.
```

### Refresh package index and install ZFS

```bash
sudo apt update && sudo apt install linux-headers-$(uname -r) zfsutils-linux -y

sudo modprobe zfs

sudo reboot
```

### Verify ZFS Installation

```bash
lsmod | grep zfs
zfs --version
zpool --version
```

### Creating and Using a ZFS Pool & Datasets
Once ZFS is installed, you can create pools (zpools) and datasets. Below is a typical example.

#### Identify disks / partitions
List available block devices:

```bash
lsblk
sudo blkid
```

Create a mirrored pool named *tank* using /dev/sda and /dev/sdb:

```bash
sudo zpool create \
  -o ashift=12 \
  -o autotrim=on \
  tank mirror /dev/sda /dev/sdb
```

Explanation:

ashift=12 sets a 4KiB sector alignment (useful for modern drives/SSDs).

autotrim=on enables automatic trimming (on SSDs).

mirror defines redundancy — you could also use raidz, raidz2, etc.

You can also check pool properties:

```bash
sudo zpool get all tank
```

Within the pool, create datasets:

```bash
sudo zfs create tank/cloud
# sudo zfs create tank/data
# sudo zfs create tank/data/projects
# sudo zfs create tank/data/backups
```

Datasets behave like sub-filesystems; you can set properties on each.

Example: enable compression and disable atime:

```bash
sudo zfs set compression=lz4 tank/data
sudo zfs set atime=off tank/data
```

#### Mountpoints
> By default, datasets are mounted under /tank/..., but you can set mountpoint property:

```bash
sudo mkdir -p /mnt/cloud
sudo zfs set mountpoint=/mnt/cloud tank/cloud
```

To list datasets and their mountpoints:

```bash
zfs list
```

#### Using snapshots & rollbacks

```bash
sudo zfs snapshot tank/data@before-update
```

Roll back:

```bash
sudo zfs rollback tank/data@before-update
```

Send/receive snapshots for backups:

```bash
sudo zfs send tank/data@before-update | ssh user@backuphost "zfs receive backup/data"
```

#### Mounting, Autostart, and Integration

> ZFS datasets are managed by ZFS itself; the mount/unmount is handled automatically by the ZFS service at boot (once ZFS is loaded). Ensure that ZFS mounting is enabled via systemd or init scripts:

```bash
sudo systemctl enable zfs-zed
sudo systemctl enable zfs-mount
sudo systemctl enable zfs-import-cache
```

PS : on Debian, the installation of zfs-zed may already set up the necessary services.

You can configure /etc/zfs/zfs-list.cache (automatically generated) for faster mounting.

---

### Querying ZFS File System Information

The zfs list command provides an extensible mechanism for viewing and querying dataset information. Both basic and complex queries are explained in this section.

#### Listing Basic ZFS Information

You can list basic dataset information by using the zfs list command with no options. This command displays the names of all datasets on the system and the values of their used, available, referenced, and mountpoint properties. For more information about these properties, see [Introducing ZFS Properties](https://docs.oracle.com/cd/E18752_01/html/819-5461/gazsu.htmlgazss.html).

For example:

```
# <b>zfs list</b>
NAME                   USED  AVAIL  REFER  MOUNTPOINT
pool                   476K  16.5G    21K  /pool
pool/clone              18K  16.5G    18K  /pool/clone
pool/home              296K  16.5G    19K  /pool/home
pool/home/marks        277K  16.5G   277K  /pool/home/marks
pool/home/marks@snap      0      -   277K  -
pool/test               18K  16.5G    18K  /test
```

You can also use this command to display specific datasets by providing the dataset name on the command line. Additionally, use the \-r option to recursively display all descendents of that dataset. For example:

```
# <b>zfs list -r pool/home/marks</b>
NAME                   USED  AVAIL  REFER  MOUNTPOINT
pool/home/marks        277K  16.5G   277K  /pool/home/marks
pool/home/marks@snap      0      -   277K  -
```

You can use the zfs list command with the mount point of a file system. For example:

```
# <b>zfs list /pool/home/marks</b>
NAME              USED  AVAIL  REFER  MOUNTPOINT
pool/home/marks   277K  16.5G   277K  /pool/home/marks
```

The following example shows how to display basic information about tank/home/chua and all of its descendent datasets:

```
# <b>zfs list -r tank/home/chua</b>
NAME                        USED  AVAIL  REFER  MOUNTPOINT 
tank/home/chua                  26.0K  4.81G  10.0K  /tank/home/chua 
tank/home/chua/projects       16K  4.81G   9.0K  /tank/home/chua/projects
tank/home/chua/projects/fs1    8K  4.81G     8K  /tank/home/chua/projects/fs1 
tank/home/chua/projects/fs2    8K  4.81G     8K  /tank/home/chua/projects/fs2
```

For additional information about the zfs list command, see [zfs(1M)](https://docs.oracle.com/cd/E18752_01/html/819-5461/gazsu.html../816-5166/zfs-1m.html#REFMAN1Mzfs-1m).

#### Creating Complex ZFS Queries

The zfs list output can be customized by using the \-o, \-t, and \-H options.

You can customize property value output by using the \-o option and a comma-separated list of desired properties. You can supply any dataset property as a valid argument. For a list of all supported dataset properties, see [Introducing ZFS Properties](https://docs.oracle.com/cd/E18752_01/html/819-5461/gazsu.htmlgazss.html). In addition to the properties defined, the \-o option list can also contain the literal name to indicate that the output should include the name of the dataset.

The following example uses zfs list to display the dataset name, along with the sharenfs and mountpoint property values.

```
# <b>zfs list -o name,sharenfs,mountpoint</b>
NAME                   SHARENFS         MOUNTPOINT
tank                   off              /tank
tank/home              on               /tank/home
tank/home/ahrens       on               /tank/home/ahrens
tank/home/bonwick      on               /tank/home/bonwick
tank/home/chua         on               /tank/home/chua
tank/home/eschrock     on               legacy
tank/home/moore        on               /tank/home/moore
tank/home/tabriz       ro               /tank/home/tabriz
```

You can use the \-t option to specify the types of datasets to display. The valid types are described in the following table.

**Table 6-2 Types of ZFS Datasets**

<table border="0" cellpadding="0" cellspacing="0" class="dkgrey1" width="100%"><tbody><tr><td><table border="0" cellpadding="0" cellspacing="1" width="100%" class="vatop"><colgroup><col width="29%"><col width="70%"></colgroup><tbody><tr><th class="columncaption" align="left" valign="top"><div class="headerpadding">Type</div></th><th class="columncaption" align="left" valign="top"><div class="headerpadding">Description</div></th></tr><tr class="yellow2"><td align="left" valign="top"><div class="pad5x10"><tt>filesystem</tt></div></td><td align="left" valign="top"><div class="pad5x10">File systems and clones</div></td></tr><tr class="yellow2"><td align="left" valign="top"><div class="pad5x10"><tt>volume</tt></div></td><td align="left" valign="top"><div class="pad5x10">Volumes</div></td></tr><tr class="yellow2"><td align="left" valign="top"><div class="pad5x10"><tt>snapshot</tt></div></td><td align="left" valign="top"><div class="pad5x10">Snapshots</div></td></tr></tbody></table></td></tr></tbody></table>

The \-t options takes a comma-separated list of the types of datasets to be displayed. The following example uses the \-t and \-o options simultaneously to show the name and used property for all file systems:

```
# <b>zfs list -t filesystem -o name,used</b>
NAME              USED
pool              476K
pool/clone         18K
pool/home         296K
pool/home/marks   277K
pool/test          18K
```

You can use the \-H option to omit the zfs list header from the generated output. With the \-H option, all white space is replaced by the Tab character. This option can be useful when you need parseable output, for example, when scripting. The following example shows the output generated from using the zfs list command with the \-H option:

```
# <b>zfs list -H -o name</b>
pool
pool/clone
pool/home
pool/home/marks
pool/home/marks@snap
pool/test
```
