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Small changes to storage driver/commands ref
Entering V's comments Signed-off-by: Mary Anthony <mary@docker.com>
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3 changed files with 20 additions and 18 deletions
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@ -1,6 +1,6 @@
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<!-- [metadata]>
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+++
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title = "Using the command line"
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title = "Docker Engine Commands"
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description = "Docker's CLI command description and usage"
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keywords = ["Docker, Docker documentation, CLI, command line"]
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[menu.main]
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@ -12,7 +12,7 @@ parent = "mn_reference"
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# The Docker commands
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This section contains reference information on using Docker's command line client. Each command has a reference page along with samples. If you are unfamiliar with the command line, you should start by reading about how to ["Use the Docker command line"](cli.md).
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This section contains reference information on using Docker's command line client. Each command has a reference page along with samples. If you are unfamiliar with the command line, you should start by reading about how to [Use the Docker command line](cli.md).
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You start the Docker daemon with the command line. How you start the daemon affects your Docker containers. For that reason you should also make sure to read the [`daemon`](daemon.md) reference page.
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@ -210,18 +210,20 @@ The procedure below will create a 90GB data volume and 4GB metadata volume to us
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5. Start the Docker daemon with the `devicemapper` storage driver and the `--storage-opt` flags.
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The `data` and `metadata` devices that you pass to the `--storage-opt` options were created in the previous steps.
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The `data` and `metadata` devices that you pass to the `--storage-opt` options were created in the previous steps.
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$ sudo docker daemon --storage-driver=devicemapper --storage-opt dm.datadev=/dev/vg-docker/data --storage-opt dm.metadatadev=/dev/vg-docker/metadata &
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[1] 2163
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[root@ip-10-0-0-75 centos]# INFO[0000] Listening for HTTP on unix (/var/run/docker.sock)
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INFO[0027] Option DefaultDriver: bridge
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INFO[0027] Option DefaultNetwork: bridge
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<output truncated>
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INFO[0027] Daemon has completed initialization
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INFO[0027] Docker daemon commit=0a8c2e3 execdriver=native-0.2 graphdriver=devicemapper version=1.8.2
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$ sudo docker daemon --storage-driver=devicemapper --storage-opt dm.datadev=/dev/vg-docker/data --storage-opt dm.metadatadev=/dev/vg-docker/metadata &
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[1] 2163
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[root@ip-10-0-0-75 centos]# INFO[0000] Listening for HTTP on unix (/var/run/docker.sock)
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INFO[0027] Option DefaultDriver: bridge
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INFO[0027] Option DefaultNetwork: bridge
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<output truncated>
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INFO[0027] Daemon has completed initialization
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INFO[0027] Docker daemon commit=0a8c2e3 execdriver=native-0.2 graphdriver=devicemapper version=1.8.2
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It is also possible to set the `--storage-driver` and `--storage-opt` flags in the Docker config file and start the daemon normally using the `service` or `systemd` commands.
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It is also possible to set the `--storage-driver` and `--storage-opt` flags in
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the Docker config file and start the daemon normally using the `service` or
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`systemd` commands.
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6. Use the `docker info` command to verify that the daemon is using `data` and `metadata` devices you created.
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@ -137,7 +137,7 @@ Once ZFS is installed and loaded, you're ready to configure ZFS for Docker.
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$ sudo zpool create -f zpool-docker /dev/xvdb
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The command creates the `zpool` and gives it the name "zpool-docker". The name is arbitrary.
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The command creates the `zpool` and gives it the name "zpool-docker". The name is arbitrary.
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2. Check that the `zpool` exists.
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@ -156,7 +156,7 @@ Once ZFS is installed and loaded, you're ready to configure ZFS for Docker.
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zpool-docker 93.5K 3.84G 19K /zpool-docker
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zpool-docker/docker 19K 3.84G 19K /var/lib/docker
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Now that you have a ZFS filesystem mounted to `/var/lib/docker`, the daemon should automatically load with the `zfs` storage driver.
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Now that you have a ZFS filesystem mounted to `/var/lib/docker`, the daemon should automatically load with the `zfs` storage driver.
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5. Start the Docker daemon.
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@ -185,9 +185,9 @@ Once ZFS is installed and loaded, you're ready to configure ZFS for Docker.
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Execution Driver: native-0.2
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[...]
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The output of the command above shows that the Docker daemon is using the
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`zfs` storage driver and that the parent dataset is the `zpool-docker/docker`
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filesystem created earlier.
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The output of the command above shows that the Docker daemon is using the
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`zfs` storage driver and that the parent dataset is the `zpool-docker/docker`
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filesystem created earlier.
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Your Docker host is now using ZFS to store to manage its images and containers.
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@ -207,7 +207,7 @@ using them with ZFS.
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* **ZFS Caching**. ZFS caches disk blocks in a memory structure called the adaptive replacement cache (ARC). The *Single Copy ARC* feature of ZFS allows a single cached copy of a block to be shared by multiple clones of a filesystem. This means that multiple running containers can share a single copy of cached block. This means that ZFS is a good option for PaaS and other high density use cases.
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- **Fragmentation**. Fragmentation is a natural byproduct of copy-on-write filesystems like ZFS. However, ZFS writes in 128K blocks and allocates *slabs* (multiple 128K blocks) to CoW operations in an attempt to reduce fragmentation. The ZFS intent log (ZIL) and the coalescing of writes (delayed writes) also help to reduce fragmentation.
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- **Fragmentation**. Fragmentation is a natural byproduct of copy-on-write filesystems like ZFS. However, ZFS writes in 128K blocks and allocates *slabs* (multiple 128K blocks) to CoW operations in an attempt to reduce fragmentation. The ZFS intent log (ZIL) and the coalescing of writes (delayed writes) also help to reduce fragmentation.
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- **Use the native ZFS driver for Linux**. Although the Docker `zfs` storage driver supports the ZFS FUSE implementation, it is not recommended when high performance is required. The native ZFS on Linux driver tends to perform better than the FUSE implementation.
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