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Initial add of zfs documentation
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Will L. Fife
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---
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category: tool
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tool: zfs
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contributors:
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- ["sarlalian", "http://github.com/sarlalian"]
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filename: LearnZfs.txt
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---
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[ZFS](http://open-zfs.org/wiki/Main_Page)
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is a rethinking of the storage stack, combining traditional file systems as well as volume
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managers into one cohesive tool. ZFS has some specific teminology that sets it appart from
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more traditional storage systems, however it has a great set of features with a focus on
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usability for systems administrators.
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## ZFS Concepts
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### Virtual Devices
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A VDEV is similar to a raid device presented by a RAID card, there are several different
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types of VDEV's that offer various advantages, including redundancy and speed. In general
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VDEV's offer better reliability and safety than a RAID card. It is discouraged to use a
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RAID setup with ZFS, as ZFS expects to directly manage the underlying disks.
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Types of VDEV's
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* stripe (a single disk, no redundancy)
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* mirror (n-way mirrors supported)
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* raidz
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* raidz1 (1-disk parity, similar to RAID 5)
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* raidz2 (2-disk parity, similar to RAID 6)
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* raidz3 (3-disk parity, no RAID analog)
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* disk
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* file (not recommended for production due to another filesystem adding unnecessary layering)
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Your data is striped across all the VDEV's present in your Storage Pool, so more VDEV's will
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increase your IOPS.
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### Storage Pools
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ZFS uses Storage Pools as an abstraction over the lower level storage provider (VDEV), allow
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you to separate the user visable file system from the physcal layout.
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### ZFS Dataset
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ZFS datasets are analagous to traditional filesystems but with many more features. They
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provide many of ZFS's advantages. Datasets support [Copy on Write](https://en.wikipedia.org/wiki/Copy-on-write)
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snapshots, quota's, compression and deduplication.
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### Limits
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One directory may contain up to 2^48 files, up to 16 exabytes each. A single storage pool
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can contain up to 256 zettabytes (2^78) of space, and can be striped across 2^64 devices. A
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single host can have 2^64 storage pools. The limits are huge.
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## Commands
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### Storage Pools
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Actions:
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* List
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* Status
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* Destroy
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* Get/Set properties
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List zpools
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```bash
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# Create a raidz zpool
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$ zpool create bucket raidz1 gpt/zfs0 gpt/zfs1 gpt/zfs2
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# List ZPools
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$ zpool list
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NAME SIZE ALLOC FREE EXPANDSZ FRAG CAP DEDUP HEALTH ALTROOT
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zroot 141G 106G 35.2G - 43% 75% 1.00x ONLINE -
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# List detailed information about a specific zpool
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$ zpool list -v zroot
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NAME SIZE ALLOC FREE EXPANDSZ FRAG CAP DEDUP HEALTH ALTROOT
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zroot 141G 106G 35.2G - 43% 75% 1.00x ONLINE -
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gptid/c92a5ccf-a5bb-11e4-a77d-001b2172c655 141G 106G 35.2G - 43% 75%
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```
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Status of zpools
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```bash
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# Get status information about zpools
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$ zpool status
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pool: zroot
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state: ONLINE
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scan: scrub repaired 0 in 2h51m with 0 errors on Thu Oct 1 07:08:31 2015
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config:
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NAME STATE READ WRITE CKSUM
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zroot ONLINE 0 0 0
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gptid/c92a5ccf-a5bb-11e4-a77d-001b2172c655 ONLINE 0 0 0
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errors: No known data errors
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# Scrubbing a zpool to correct any errors
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$ zpool scrub zroot
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$ zpool status -v zroot
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pool: zroot
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state: ONLINE
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scan: scrub in progress since Thu Oct 15 16:59:14 2015
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39.1M scanned out of 106G at 1.45M/s, 20h47m to go
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0 repaired, 0.04% done
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config:
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NAME STATE READ WRITE CKSUM
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zroot ONLINE 0 0 0
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gptid/c92a5ccf-a5bb-11e4-a77d-001b2172c655 ONLINE 0 0 0
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errors: No known data errors
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```
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Properties of zpools
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```bash
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# Getting properties from the pool properties can be user set or system provided.
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$ zpool get all zroot
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NAME PROPERTY VALUE SOURCE
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zroot size 141G -
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zroot capacity 75% -
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zroot altroot - default
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zroot health ONLINE -
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...
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# Setting a zpool property
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$ zpool set comment="Storage of mah stuff" zroot
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$ zpool get comment
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NAME PROPERTY VALUE SOURCE
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tank comment - default
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zroot comment Storage of mah stuff local
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```
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Remove zpool
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```bash
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$ zpool destroy test
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```
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### Datasets
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Actions:
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* Create
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* List
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* Rename
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* Delete
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* Get/Set properties
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Create datasets
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```bash
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# Create dataset
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$ zfs create tank/root/data
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$ mount | grep data
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tank/root/data on /data (zfs, local, nfsv4acls)
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# Create child dataset
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$ zfs create tank/root/data/stuff
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$ mount | grep data
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tank/root/data on /data (zfs, local, nfsv4acls)
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tank/root/data/stuff on /data/stuff (zfs, local, nfsv4acls)
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# Create Volume
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$ zfs create -V zroot/win_vm
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$ zfs list zroot/win_vm
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NAME USED AVAIL REFER MOUNTPOINT
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tank/win_vm 4.13G 17.9G 64K -
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```
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List datasets
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```bash
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# List all datasets
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$ zfs list
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NAME USED AVAIL REFER MOUNTPOINT
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zroot 106G 30.8G 144K none
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zroot/ROOT 18.5G 30.8G 144K none
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zroot/ROOT/10.1 8K 30.8G 9.63G /
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zroot/ROOT/default 18.5G 30.8G 11.2G /
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zroot/backup 5.23G 30.8G 144K none
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zroot/home 288K 30.8G 144K none
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...
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# List a specific dataset
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$ zfs list zroot/home
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NAME USED AVAIL REFER MOUNTPOINT
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zroot/home 288K 30.8G 144K none
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# List snapshots
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$ zfs list -t snapshot
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zroot@daily-2015-10-15 0 - 144K -
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zroot/ROOT@daily-2015-10-15 0 - 144K -
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zroot/ROOT/default@daily-2015-10-15 0 - 24.2G -
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zroot/tmp@daily-2015-10-15 124K - 708M -
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zroot/usr@daily-2015-10-15 0 - 144K -
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zroot/home@daily-2015-10-15 0 - 11.9G -
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zroot/var@daily-2015-10-15 704K - 1.42G -
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zroot/var/log@daily-2015-10-15 192K - 828K -
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zroot/var/tmp@daily-2015-10-15 0 - 152K -
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```
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Rename datasets
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```bash
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$ zfs rename tank/root/home tank/root/old_home
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$ zfs rename tank/root/new_home tank/root/home
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```
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Delete dataset
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```bash
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# Datasets cannot be deleted if they have any snapshots
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zfs destroy tank/root/home
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```
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Get / set properties of a dataset
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```bash
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# Get all properties
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$ zfs get all zroot/usr/home │157 # Create Volume
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NAME PROPERTY VALUE SOURCE │158 $ zfs create -V zroot/win_vm
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zroot/home type filesystem - │159 $ zfs list zroot/win_vm
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zroot/home creation Mon Oct 20 14:44 2014 - │160 NAME USED AVAIL REFER MOUNTPOINT
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zroot/home used 11.9G - │161 tank/win_vm 4.13G 17.9G 64K -
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zroot/home available 94.1G - │162 ```
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zroot/home referenced 11.9G - │163
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zroot/home mounted yes -
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...
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# Get property from dataset
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$ zfs get compression zroot/usr/home
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NAME PROPERTY VALUE SOURCE
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zroot/home compression off default
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# Set property on dataset
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$ zfs set compression=gzip-9 mypool/lamb
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# Get a set of properties from all datasets
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$ zfs list -o name,quota,reservation
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NAME QUOTA RESERV
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zroot none none
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zroot/ROOT none none
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zroot/ROOT/default none none
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zroot/tmp none none
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zroot/usr none none
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zroot/home none none
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zroot/var none none
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...
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```
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### Snapshots
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ZFS snapshots are one of the things about zfs that are a really big deal
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* The space they take up is equal to the difference in data between the filesystem and its snapshot
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* Creation time is only seconds
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* Recovery is as fast as you can write data.
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* They are easy to automate.
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Actions:
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* Create
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* Delete
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* Rename
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* Access snapshots
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* Send / Receive
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* Clone
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Create snapshots
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```bash
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# Create a snapshot of a single dataset
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zfs snapshot tank/home/sarlalian@now
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# Create a snapshot of a dataset and its children
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$ zfs snapshot -r tank/home@now
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$ zfs list -t snapshot
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NAME USED AVAIL REFER MOUNTPOINT
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tank/home@now 0 - 26K -
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tank/home/sarlalian@now 0 - 259M -
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tank/home/alice@now 0 - 156M -
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tank/home/bob@now 0 - 156M -
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...
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Destroy snapshots
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```bash
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# How to destroy a snapshot
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$ zfs destroy tank/home/sarlalian@now
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# Delete a snapshot on a parent dataset and its children
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$ zfs destroy -r tank/home/sarlalian@now
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```
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Renaming Snapshots
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```bash
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# Rename a snapshot
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$ zfs rename tank/home/sarlalian@now tank/home/sarlalian@today
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$ zfs rename tank/home/sarlalian@now today
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# zfs rename -r tank/home@now @yesterday
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```
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Accessing snapshots
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```bash
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# CD Into a snapshot directory
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$ cd /home/.zfs/snapshot/
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```
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Sending and Receiving
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```bash
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# Backup a snapshot to a file
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$ zfs send tank/home/sarlalian@now | gzip > backup_file.gz
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# Send a snapshot to another dataset
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$ zfs send tank/home/sarlalian@now | zfs recv backups/home/sarlalian
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# Send a snapshot to a remote host
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$ zfs send tank/home/sarlalian@now | ssh root@backup_server 'zfs recv tank/home/sarlalian'
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# Send full dataset with snapshos to new host
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$ zfs send -v -R tank/home@now | ssh root@backup_server 'zfs recv tank/home'
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```
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Cloneing Snapshots
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```bash
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# Clone a snapshot
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$ zfs clone tank/home/sarlalian@now tank/home/sarlalian_new
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# Promoting the clone so it is no longer dependent on the snapshot
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$ zfs promote tank/home/sarlalian_new
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```
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