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| -rw-r--r-- | src/SUMMARY.md | 1 | ||||
| -rw-r--r-- | src/linux/README.md | 1 | ||||
| -rw-r--r-- | src/linux/zfs.md | 249 |
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diff --git a/src/SUMMARY.md b/src/SUMMARY.md index 889118a..fb22e69 100644 --- a/src/SUMMARY.md +++ b/src/SUMMARY.md @@ -59,6 +59,7 @@ - [swap](./linux/swap.md) - [input](./linux/input.md) - [acl](./linux/acl.md) + - [zfs](./linux/zfs.md) - [Network](./network/README.md) - [tcpdump](./network/tcpdump.md) diff --git a/src/linux/README.md b/src/linux/README.md index ba63829..4edddde 100644 --- a/src/linux/README.md +++ b/src/linux/README.md @@ -7,3 +7,4 @@ - [swap](./swap.md) - [input](./input.md) - [acl](./acl.md) +- [zfs](./zfs.md) diff --git a/src/linux/zfs.md b/src/linux/zfs.md new file mode 100644 index 0000000..e52874d --- /dev/null +++ b/src/linux/zfs.md @@ -0,0 +1,249 @@ +# zfs + +Pools are managed with the [`zpool(8)`][man-zpool] command and have the +following hierarchy: +- `pool`: consists of one or more virtual devices (`vdev`) +- `vdev`: consists of one or more physical devices (`dev`) and come in + different kinds such as [`disk`, `mirror`, `raidzX`, ...][man-zpool-vdev] + - `disk`: single physical disk (`vdev == dev`) + - `mirror`: data is identically replicated on all `devs` (requires at least 2 + physical devices). + +Data stored in a pool is distributed and stored across all `vdevs` by zfs. +Therefore a total failure of a single `vdev` can lead to total loss of a pool. + +A `dataset` is a logical volume which can be created on top of a `pool`. Each +`dataset` can be configured with its own set of `properties` like +[`encryption`, `quota`, ...][man-zfsprops]. +Datasets are managed with the [`zfs(8)`][man-zfs] command. + +## zfs pool management +Pools are by default mounted at `/<POOL>`. + +### Create, modify and destroy zfs pools +```bash +# Create a pool MOOSE with a two mirror vdevs. +zpool create moose mirror <dev1> <dev2> mirror <dev3> <dev4>.. + +# Add new raidz1 vdev to a pool. +zpool add moose raidz1 <devA> <devB> <devC>.. + +# Remove a vdev from a pool. +zpool remove moose <vdevX> + +# Destroy a pool. +zpool destroy moose +``` +> For stable device names in small home setups it is recommended to use names +> from [`/dev/disk/by-id`][faq-which-dev]. + +### Inspect zfs pools +```bash +# Show status of all pools or a single one. +zpool status [<pool>] + +# Show information / statistics about pools or single one. +zpool list [<pool>] + +# Show statistics for all devices. +zpool list -v + +# Show command history for pools. +zpool history +``` + +### Modify `vdevs` +```bash +# vdev MIRROR-0 with two devs. +zpool status + NAME STATE READ WRITE CKSUM + moose ONLINE 0 0 0 + mirror-0 ONLINE 0 0 0 + virtio-200 ONLINE 0 0 0 + virtio-300 ONLINE 0 0 0 + +# Attach new device to an existing vdev. +zpool attach moose virtio-200 virtio-400 + +# vdev MIRROR-0 with three devs. +zpool status + NAME STATE READ WRITE CKSUM + moose ONLINE 0 0 0 + mirror-0 ONLINE 0 0 0 + virtio-200 ONLINE 0 0 0 + virtio-300 ONLINE 0 0 0 + virtio-400 ONLINE 0 0 0 + +# Detach device from vdev. +zpool detach moose virtio-200 +``` + +### Replace faulty disk +```bash +# MIRROR-0 is degraded as one disk failed, but still intact. +zpool status + NAME STATE READ WRITE CKSUM + moose DEGRADED 0 0 0 + mirror-0 DEGRADED 0 0 0 + virtio-200 UNAVAIL 0 0 0 invalid label + virtio-300 ONLINE 0 0 0 + +# Replace faulty disk, in mirror. +# No data is lost since mirror still has one good disk. +zpool replace moose virtio-200 virtio-400 + +# MIRROR-0 back in ONLINE (good) state. +zpool status + NAME STATE READ WRITE CKSUM + moose ONLINE 0 0 0 + mirror-0 ONLINE 0 0 0 + virtio-400 ONLINE 0 0 0 + virtio-300 ONLINE 0 0 0 +``` + +### Import or export zfs pools +When moving pools between hosts, the pool must be `exported` on the currently +active host and `imported` on the new host. + +```bash +# Export a pool called MOOSE. +zpool export moose + +# List pools that can be imported using BY-ID deivce names (for example). +zpool import -d /dev/disk/by-id + +# Import pool MOOSE using BY-ID device names (for example). +zpool import -d /dev/disk/by-id moose +``` +> Device names used by an existing pool can be changed by [exporting and +> importing][faq-rename-dev] a pool again. + +## zfs dataset management +Datasets are by default mounted at `/<POOL>/<DATASET>`. + +### Create and destroy zfs datasets +```bash +# Create dataset FOO on pool MOOSE. +zfs create moose/foo + +# Destroy dataset. +zfs destroy moose/foo +``` + +### List all zfs datasets +```bash +# List all zfs datasets. +zfs list +``` + +### Mount zfs datasets +```bash +# List currently mounted datasets. +zfs mount + +# Mount dataset. +zfs mount moose/foo + +# Unmount dataset. +zfs unmount moose/foo +``` + +### Encrypted datasets +Encryption is a readonly property, can only be set when creating a dataset. + +```bash +# Create encrypted dataset ENC on pool MOOSE. +zfs create -o encryption=on -o keyformat=passphrase moose/foo + +# Mount encrypte dataset (if key is not loaded). +zfs mount -l moose/foo + +# Unmount dataset and unload encryption key (unload is optional). +zfs umount -u moose/foo +``` + +### Manage zfs encryption keys +```bash +# Preload encryption key for dataset. +zfs load-key moose/foo + +# Preload encryption key for all datasets. +zfs load-key -a + +# Change encryption key for dataset. +zfs change-key moose/foo + +# Unload encryption key for dataset. +zfs unload-key moose/foo +``` + +### Manage dataset properties +```bash +# Get all properties for dataset. +zfs get quota moose/foo + +# Get single property for dataset. +zfs get all moose/foo + +# Get single property for all datasets. +zfs get quota + +# Set property on dataset. +zfs set quota=10G moose/foo +``` + +### Snapshots +```bash +# Create snapshot called V2 for dataset moose/foo. +zfs snapshot moose/foo@v2 + +# List all snapshots. +zfs list -t snapshot + +# Make .zfs direcotry visible in the root of the dataset. +zfs set snapdir=visible moose/foo + +# Browse available snapshots in visible .zfs direcotry (readonly). +ls /moose/foo/.zfs/snapshot +v1/ v2/ + +# Create a new dataset based on the V1 snapshot +zfs clone moose/foo@v1 moose/foov1 + +# Destroy snapshot. +zfs destroy moose/foo@v1 +``` + +### Access control list +Focus on [posix acl](./acl.md). +```bash +# Set the ACL type for the FOO dataset to POSIXACL. +zfs set acltype=posixacl moose/foo + +# Get the ACL type of a given dataset. +zfs get acltype moose/foo +``` +> For performance reasons it is recommended to also set `zfs set xattr=sa +> moose/foo` [[ref][zfs-xattr-perf]]. + +## Example: zfs pool import during startup (`systemd`) +The default zpool cache file is `/etc/zfs/zpool.cache`. When pools are imported +the cache is updated. + +Enable the following targets / services to automatically import pools from the +cache. +```bash +systemctl list-dependencies + ... + └─zfs.target + └─zfs-import.target + └─zfs-import-cache.service +``` + +[man-zpool]: https://openzfs.github.io/openzfs-docs/man/8/zpool.8.html +[man-zpool-vdev]: https://openzfs.github.io/openzfs-docs/man/7/zpoolconcepts.7.html#Virtual_Devices_(vdevs) +[man-zfs]: https://openzfs.github.io/openzfs-docs/man/8/zfs.8.html +[man-zfsprops]: https://openzfs.github.io/openzfs-docs/man/7/zfsprops.7.html +[faq-which-dev]: https://openzfs.github.io/openzfs-docs/Project%20and%20Community/FAQ.html#selecting-dev-names-when-creating-a-pool-linux +[faq-rename-dev]: https://openzfs.github.io/openzfs-docs/Project%20and%20Community/FAQ.html#changing-dev-names-on-an-existing-pool +[zfs-xattr-perf]: https://github.com/openzfs/zfs/issues/170#issuecomment-27348094 |