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Rewrites to Ubuntu installation 

Fixes #203
This commit is contained in:
Misty Stanley-Jones 2016-11-18 09:36:07 -08:00
parent 01e491d860
commit 718296c37d
1 changed files with 369 additions and 228 deletions
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engine/installation/linux/ubuntulinux.md
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@ -14,58 +14,61 @@ Docker is supported on these Ubuntu operating systems:
- Ubuntu Trusty 14.04 (LTS) - Ubuntu Trusty 14.04 (LTS)
- Ubuntu Precise 12.04 (LTS) - Ubuntu Precise 12.04 (LTS)
This page instructs you to install using Docker-managed release packages and This page instructs you to install Docker on Ubuntu, using packages provided by
installation mechanisms. Using these packages ensures you get the latest official Docker. Using these packages ensures you get the latest official
release of Docker. If you are required to install using Ubuntu-managed packages, release of Docker. If you are required to install using Ubuntu-managed packages,
consult the Ubuntu documentation. consult the Ubuntu documentation. Some files and commands may be different if
you use Ubuntu-managed packages.
>**Note**: Ubuntu Utopic 14.10 and 15.04 exist in Docker's `APT` repository but >**Note**: Ubuntu Utopic 14.10 and 15.04 exist in Docker's `APT` repository but
are no longer officially supported. are no longer officially supported.
## Prerequisites ## Prerequisites
Docker requires a 64-bit installation regardless of your Ubuntu version. Docker has two important installation requirements:
Additionally, your kernel must be 3.10 at minimum. The latest 3.10 minor version
or a newer maintained version are also acceptable.
Kernels older than 3.10 lack some of the features required to run Docker - Docker only works on a 64-bit Linux installation.
containers. These older versions have known bugs which cause data loss - Docker requires version 3.10 or higher of the Linux kernel. Kernels older than
and frequently panic under certain conditions. 3.10 lack some of the features required to run Docker containers and contain
known bugs which cause data loss and frequently panic under certain conditions.
To check your current kernel version, open a terminal and use `uname -r` to To check your current kernel version, open a terminal and use `uname -r` to
display your kernel version: display your kernel version:
$ uname -r ```bash
3.11.0-15-generic $ uname -r
3.11.0-15-generic
>**Note**: If you previously installed Docker using `APT`, make sure you update ```
your `APT` sources to the new Docker repository.
### Update your apt sources ### Update your apt sources
Docker's `APT` repository contains Docker 1.7.1 and higher. To set `APT` to use To set `APT` to use packages from the Docker repository:
packages from the Docker repository:
1. Log into your machine as a user with `sudo` or `root` privileges. 1. Log into your machine as a user with `sudo` or `root` privileges.
2. Open a terminal window. 2. Open a terminal window.
3. Update package information, ensure that APT works with the `https` method, and that CA certificates are installed. 3. Update package information, ensure that APT works with the `https` method,
and that CA certificates are installed.
```bash ```bash
$ sudo apt-get update $ sudo apt-get update
$ sudo apt-get install apt-transport-https ca-certificates $ sudo apt-get install apt-transport-https ca-certificates
``` ```
4. Add the new `GPG` key. 4. Add the new `GPG` key. This commands downloads the key with the ID
`58118E89F3A912897C070ADBF76221572C52609D` from the keyserver
`hkp://ha.pool.sks-keyservers.net:80` and adds it to the `adv` keychain.
For more info, see the output of `man apt-key`.
```bash ```bash
$ sudo apt-key adv --keyserver hkp://ha.pool.sks-keyservers.net:80 --recv-keys 58118E89F3A912897C070ADBF76221572C52609D $ sudo apt-key adv \
--keyserver hkp://ha.pool.sks-keyservers.net:80 \
--recv-keys 58118E89F3A912897C070ADBF76221572C52609D
``` ```
5. Find the entry for your Ubuntu operating system. 5. Find the entry in the table below which corresponds to your Ubuntu version.
This determines where APT will search for Docker packages. When possible,
The entry determines where APT will search for packages. The possible entries run a long-term support (LTS) edition of Ubuntu.
are:
| Ubuntu version | Repository | | Ubuntu version | Repository |
| ------------------- | ----------------------------------------------------------- | | ------------------- | ----------------------------------------------------------- |
@ -116,36 +119,33 @@ packages from the Docker repository:
500 https://apt.dockerproject.org/repo/ ubuntu-trusty/main amd64 Packages 500 https://apt.dockerproject.org/repo/ ubuntu-trusty/main amd64 Packages
1.12.0-0~trusty 0 1.12.0-0~trusty 0
500 https://apt.dockerproject.org/repo/ ubuntu-trusty/main amd64 Packages 500 https://apt.dockerproject.org/repo/ ubuntu-trusty/main amd64 Packages
1.11.2-0~trusty 0
500 https://apt.dockerproject.org/repo/ ubuntu-trusty/main amd64 Packages
1.11.1-0~trusty 0
500 https://apt.dockerproject.org/repo/ ubuntu-trusty/main amd64 Packages
``` ```
From now on when you run `apt-get upgrade`, `APT` pulls from the new repository. From now on when you run `apt-get upgrade`, `APT` pulls from the new repository.
### Prerequisites by Ubuntu Version ### Prerequisites by Ubuntu Version
- Ubuntu Xenial 16.04 (LTS) #### Ubuntu Xenial 16.04 (LTS), Wily 15.10, Trusty 14.04 (LTS)
- Ubuntu Wily 15.10
- Ubuntu Trusty 14.04 (LTS)
For Ubuntu Trusty, Wily, and Xenial, it's recommended to install the For Ubuntu Trusty, Wily, and Xenial, install the `linux-image-extra-*` kernel
`linux-image-extra-*` kernel packages. The `linux-image-extra-*` packages packages, which allows you use the `aufs` storage driver.
allows you use the `aufs` storage driver.
To install the `linux-image-extra-*` packages: To install the `linux-image-extra-*` packages:
1. Open a terminal on your Ubuntu host. 1. Open a terminal on your Ubuntu host.
2. Update your package manager. 2. Update your package manager.
$ sudo apt-get update ```bash
$ sudo apt-get update
```
3. Install the recommended packages. 3. Install the recommended packages.
$ sudo apt-get install linux-image-extra-$(uname -r) linux-image-extra-virtual ```bash
$ sudo apt-get install linux-image-extra-$(uname -r) linux-image-extra-virtual
```
4. Go ahead and install Docker. 4. Go ahead and [install Docker](ubuntulinux.md#install).
#### Ubuntu Precise 12.04 (LTS) #### Ubuntu Precise 12.04 (LTS)
@ -153,180 +153,248 @@ For Ubuntu Precise, Docker requires the 3.13 kernel version. If your kernel
version is older than 3.13, you must upgrade it. Refer to this table to see version is older than 3.13, you must upgrade it. Refer to this table to see
which packages are required for your environment: which packages are required for your environment:
<table> | Package | Description |
<thead> | --------------------------------- | ----------- |
<tr> | `linux-image-generic-lts-trusty` | Generic Linux kernel image. This kernel has AUFS built in. This is required to run Docker. |
<th>Package</th> | `linux-headers-generic-lts-trusty`| Allows packages such as ZFS and VirtualBox guest additions which depend on them. If you didn't install the headers for your existing kernel, then you can skip these headers for the"trusty" kernel. If you're unsure, you should include this package for safety. |
<th>Description</th> | `xserver-xorg-lts-trusty` | Optional in non-graphical environments without Unity/Xorg. **Required** when running Docker on machine with a graphical environment. |
</tr> | `ligbl1-mesa-glx-lts-trusty` | To learn more about the reasons for these packages, read the installation instructions for backported kernels, specifically the [LTS Enablement Stack](https://wiki.ubuntu.com/Kernel/LTSEnablementStack). Refer to note 5 under each version. |
</thead>
<tbody>
<tr>
<td><b style="white-space: nowrap">linux-image-generic-lts-trusty</b></td>
<td>
Generic Linux kernel image. This kernel has AUFS built in. This is
required to run Docker.
</td>
</tr>
<tr>
<td><b style="white-space: nowrap">linux-headers-generic-lts-trusty</b></td>
<td>
Allows packages such as ZFS and VirtualBox guest additions which depend
on them. If you didn't install the headers for your existing kernel, then
you can skip these headers for the"trusty" kernel. If you're unsure, you
should include this package for safety.
</td>
</tr>
<tr>
<td><b style="white-space: nowrap">xserver-xorg-lts-trusty</b></td>
<td rowspan="2">
Optional in non-graphical environments without Unity/Xorg.
<b>Required</b> when running Docker on machine with a graphical
environment.<br /><br />
To learn more about the reasons for these packages, read the installation
instructions for backported kernels, specifically the <a
href="https://wiki.ubuntu.com/Kernel/LTSEnablementStack"
target="_blank">LTS Enablement Stack</a> &mdash; refer to note 5 under each
version.
</td>
</tr>
<tr>
<td><b style="white-space: nowrap">libgl1-mesa-glx-lts-trusty</b></td>
</tr>
</tbody>
</table>
To upgrade your kernel and install the additional packages, do the following: To upgrade your kernel and install the additional packages, do the following:
1. Open a terminal on your Ubuntu host. 1. Open a terminal on your Ubuntu host.
2. Update your package manager. 2. Update your package manager.
$ sudo apt-get update ```bash
$ sudo apt-get update
```
3. Install both the required and optional packages. 3. Install both the required and optional packages.
$ sudo apt-get install linux-image-generic-lts-trusty ```bash
$ sudo apt-get install linux-image-generic-lts-trusty
```
Depending on your environment, you may install more as described in the preceding table. Repeat this step for other packages you need to install.
4. Reboot your host. 4. Reboot your host to use the updated kernel.
$ sudo reboot ```bash
$ sudo reboot
```
5. After your system reboots, go ahead and install Docker. 5. After your system reboots, go ahead and
[install Docker](ubuntulinux.md#install).
## Install ## Install the latest version
Make sure you have installed the prerequisites for your Ubuntu version. Make sure you have satisfied all the
[prerequisites](ubuntulinux.md#prerequisites), then follow these steps.
Then, >**Note**: For production systems, it is recommended that you
install Docker using the following: [install a specific version](ubuntulinux.md#install-a-specific-version) so that
you do not accidentally update Docker. You should plan upgrades for production
systems carefully.
1. Log into your Ubuntu installation as a user with `sudo` privileges. 1. Log into your Ubuntu installation as a user with `sudo` privileges.
2. Update your `APT` package index. 2. Update your `APT` package index.
$ sudo apt-get update ```bash
$ sudo apt-get update
```
3. Install Docker.
3. Install Docker. ```bash
$ sudo apt-get install docker-engine
```
$ sudo apt-get install docker-engine 4. Start the `docker` daemon.
4. Start the `docker` daemon. ```bash
$ sudo service docker start
```
$ sudo service docker start 5. Verify that `docker` is installed correctly by running the `hello-world`
image.
5. Verify `docker` is installed correctly. ```bash
$ sudo docker run hello-world
$ sudo docker run hello-world ```
This command downloads a test image and runs it in a container. When the This command downloads a test image and runs it in a container. When the
container runs, it prints an informational message. Then, it exits. container runs, it prints an informational message and exits.
## Install a specific version
To install a specific version of `docker-engine`:
1. List all available versions using `apt-cache madison`:
```bash
$ apt-cache madison docker-engine
docker-engine | 1.12.3-0~xenial | https://apt.dockerproject.org/repo ubuntu-xenial/main amd64 Packages
docker-engine | 1.12.2-0~xenial | https://apt.dockerproject.org/repo ubuntu-xenial/main amd64 Packages
docker-engine | 1.12.1-0~xenial | https://apt.dockerproject.org/repo ubuntu-xenial/main amd64 Packages
docker-engine | 1.12.0-0~xenial | https://apt.dockerproject.org/repo ubuntu-xenial/main amd64 Packages
docker-engine | 1.11.2-0~xenial | https://apt.dockerproject.org/repo ubuntu-xenial/main amd64 Packages
docker-engine | 1.11.1-0~xenial | https://apt.dockerproject.org/repo ubuntu-xenial/main amd64 Packages
docker-engine | 1.11.0-0~xenial | https://apt.dockerproject.org/repo ubuntu-xenial/main amd64 Packages
```
2. The second field is the version string. To install exactly `1.12.0-0~xenial`,
append it after the package name in the `apt-get install` command, separated
from the package name by an equals sign (`=`).
```bash
$ sudo apt-get install docker-engine=1.12.0-0~xenial
```
If you already have a newer version installed, you will be prompted to
downgrade Docker. Otherwise, the specific version will be installed.
3. Follow steps 4 and 5 of
[Install the latest version](ubuntulinux.md#install-the-latest-version).
## Install a pre-release version
If you want to test Docker on Ubuntu, on a non-production system, follow these
steps. To install a stable released version of Docker afterward, you will need
to revert to the previous configuration.
1. Edit `/etc/apt/sources.list.d/docker.list`.
```bash
$ sudo nano /etc/apt/sources.list.d/docker.list
```
Change `main` to `testing` at the end of the top line. Save and close the
file.
2. Update the package list.
```bash
$ sudo apt-get update
```
3. List the available testing versions.
```bash
$ sudo apt-cache madison docker-engine
```
4. Install a specific version following the same procedure as
[Install a specific version](ubuntulinux.md#install-a-specific-version).
## Optional configurations ## Optional configurations
This section contains optional procedures for configuring your Ubuntu to work This section contains optional procedures for configuring Ubuntu to work better
better with Docker. with Docker.
* [Create a docker group](ubuntulinux.md#create-a-docker-group) * [Manager Docker as a non-root user](ubuntulinux.md#manage-docker-as-a-non-root-user)
* [Adjust memory and swap accounting](ubuntulinux.md#adjust-memory-and-swap-accounting) * [Adjust memory and swap accounting](ubuntulinux.md#adjust-memory-and-swap-accounting)
* [Enable UFW forwarding](ubuntulinux.md#enable-ufw-forwarding) * [Enable UFW forwarding](ubuntulinux.md#enable-ufw-forwarding)
* [Configure a DNS server for use by Docker](ubuntulinux.md#configure-a-dns-server-for-use-by-docker) * [Configure a DNS server for use by Docker](ubuntulinux.md#configure-a-dns-server-for-use-by-docker)
* [Configure Docker to start on boot](ubuntulinux.md#configure-docker-to-start-on-boot) * [Configure Docker to start on boot](ubuntulinux.md#configure-docker-to-start-on-boot)
### Create a Docker group ### Manage Docker as a non-root user
The `docker` daemon binds to a Unix socket instead of a TCP port. By default The `docker` daemon binds to a Unix socket instead of a TCP port. By default
that Unix socket is owned by the user `root` and other users can access it with that Unix socket is owned by the user `root` and other users can only access it
`sudo`. For this reason, `docker` daemon always runs as the `root` user. using `sudo`. The `docker` daemon always runs as the `root` user.
To avoid having to use `sudo` when you use the `docker` command, create a Unix If you don't want to use `sudo` when you use the `docker` command, create a Unix
group called `docker` and add users to it. When the `docker` daemon starts, it group called `docker` and add users to it. When the `docker` daemon starts, it
makes the ownership of the Unix socket read/writable by the `docker` group. makes the ownership of the Unix socket read/writable by the `docker` group.
>**Warning**: The `docker` group is equivalent to the `root` user; For details >**Warning**: The `docker` group is equivalent to the `root` user. For details
>on how this impacts security in your system, see [*Docker Daemon Attack on how this impacts security in your system, see [*Docker Daemon Attack
>Surface*](../../security/security.md#docker-daemon-attack-surface) for details. Surface*](../../security/security.md#docker-daemon-attack-surface) for details.
To create the `docker` group and add your user: To create the `docker` group and add your user:
1. Log into Ubuntu as a user with `sudo` privileges. 1. Log into Ubuntu as a user with `sudo` privileges.
2. Create the `docker` group. 2. Create the `docker` group.
```bash
$ sudo groupadd docker
```
$ sudo groupadd docker 3. Add your user to the `docker` group.
3. Add your user to `docker` group. ```bash
$ sudo usermod -aG docker $USER
```
$ sudo usermod -aG docker $USER 4. Log out and log back in so that your group membership is re-evaluated.
4. Log out and log back in. 5. Verify that you can `docker` commands without `sudo`.
This ensures your user is running with the correct permissions. ```bash
$ docker run hello-world
```
5. Verify your work by running `docker` without `sudo`. If this fails, you will see an error:
$ docker run hello-world
If this fails with a message similar to this:
```none
Cannot connect to the Docker daemon. Is 'docker daemon' running on this host? Cannot connect to the Docker daemon. Is 'docker daemon' running on this host?
```
Check that the `DOCKER_HOST` environment variable is not set for your shell. Check whether the `DOCKER_HOST` environment variable is set for your shell.
If it is, unset it.
### Adjust memory and swap accounting ```bash
$ env | grep DOCKER_HOST
```
When users run Docker, they may see these messages when working with an image: If it is set, the above command will return a result. If so, unset it.
WARNING: Your kernel does not support cgroup swap limit. WARNING: Your ```bash
kernel does not support swap limit capabilities. Limitation discarded. $ unset DOCKER_HOST
```
To prevent these messages, enable memory and swap accounting on your You may need to edit your environment in files such as `~/.bashrc` or
system. Enabling memory and swap accounting does induce both a memory `~/.profile` to prevent the `DOCKER_HOST` variable from being set
overhead and a performance degradation even when Docker is not in erroneously.
use. The memory overhead is about 1% of the total available
memory. The performance degradation is roughly 10%.
To enable memory and swap on system using GNU GRUB (GNU GRand Unified ### Enable memory and swap accounting
Bootloader), do the following:
1. Log into Ubuntu as a user with `sudo` privileges. You may see messages similar to the following when working with an image:
2. Edit the `/etc/default/grub` file. ```none
WARNING: Your kernel does not support cgroup swap limit. WARNING: Your
kernel does not support swap limit capabilities. Limitation discarded.
```
3. Set the `GRUB_CMDLINE_LINUX` value as follows: If you don't care about these capabilities, you can ignore the warning. You can
enable these capabilities in your kernel by following these instructions. Memory
and swap accounting incur an overhead of about 1% of the total available
memory and a 10% overall performance degradation, even if Docker is not running.
GRUB_CMDLINE_LINUX="cgroup_enable=memory swapaccount=1" 1. Log into Ubuntu as a user with `sudo` privileges.
4. Save and close the file. 2. Edit the `/etc/default/grub` file.
5. Update GRUB. 3. Add or edit the `GRUB_CMDLINE_LINUX` line to add the following two key-value
pairs:
$ sudo update-grub ```none
GRUB_CMDLINE_LINUX="cgroup_enable=memory swapaccount=1"
```
6. Reboot your system. Save and close the file.
4. Update GRUB.
```bash
$ sudo update-grub
```
If your GRUB configuration file has incorrect syntax, an error will occur.
In this case, steps 3 and 4.
6. Reboot your system. Memory and swap accounting are enabled and the warning
does not occur.
### Enable UFW forwarding ### Enable UFW forwarding
@ -334,147 +402,220 @@ Bootloader), do the following:
If you use [UFW (Uncomplicated Firewall)](https://help.ubuntu.com/community/UFW) If you use [UFW (Uncomplicated Firewall)](https://help.ubuntu.com/community/UFW)
on the same host as you run Docker, you'll need to do additional configuration. on the same host as you run Docker, you'll need to do additional configuration.
Docker uses a bridge to manage container networking. By default, UFW drops all Docker uses a bridge to manage container networking. By default, UFW drops all
forwarding traffic. As a result, for Docker to run when UFW is forwarding traffic. You must set UFW's forwarding policy appropriately.
enabled, you must set UFW's forwarding policy appropriately.
Also, UFW's default set of rules denies all incoming traffic. If you want to In addition, UFW blocks all incoming traffic by default. If you want to access
reach your containers from another host allow incoming connections on the Docker the Docker Remote API from another host and you have enabled remote access, you
port. The Docker port defaults to `2376` if TLS is enabled or `2375` when it is need to configure UFW to allow incoming connections on the Docker port, which
not. If TLS is not enabled, communication is unencrypted. By default, Docker defaults to `2376` if TLS encrypted transport is enabled or `2375` otherwise. By
runs without TLS enabled. default, Docker runs **without** TLS enabled. If you do not use TLS, you are
strongly discouraged from allowing access to the Docker Remote API from remote
hosts, to prevent remote privilege-escalation attacks.
To configure UFW and allow incoming connections on the Docker port: To configure UFW and allow incoming connections on the Docker port:
1. Log into Ubuntu as a user with `sudo` privileges. 1. Log into Ubuntu as a user with `sudo` privileges.
2. Verify that UFW is installed and enabled. 2. Verify that UFW is enabled.
$ sudo ufw status ```bash
$ sudo ufw status
```
3. Open the `/etc/default/ufw` file for editing. If `ufw` is not enabled, the remaining steps will not be helpful.
$ sudo nano /etc/default/ufw 3. Edit the UFW configuration file, which is usually `/etc/default/ufw` or
`/etc/sysconfig/ufw`. Set the `DEFAULT_FORWARD_POLICY` policy to `ACCEPT`.
4. Set the `DEFAULT_FORWARD_POLICY` policy to: ```none
DEFAULT_FORWARD_POLICY="ACCEPT"
```
DEFAULT_FORWARD_POLICY="ACCEPT" Save and close the file.
5. Save and close the file. 4. If you need to enable access to the Docker Remote API from external hosts
and understand the security implications (see the section before this
procedure), then configure UFW to allow incoming connections on the Docker port,
which is 2375 if you do not use TLS, and 2376 if you do.
6. Reload UFW to use the new setting. ```bash
$ sudo ufw allow 2376/tcp
```
$ sudo ufw reload 5. Reload UFW.
```bash
7. Allow incoming connections on the Docker port. $ sudo ufw reload
```
$ sudo ufw allow 2375/tcp
### Configure a DNS server for use by Docker ### Configure a DNS server for use by Docker
Systems that run Ubuntu or an Ubuntu derivative on the desktop typically use Ubuntu systems which use `networkmanager` use a `dnsmasq` instance that runs on
`127.0.0.1` as the default `nameserver` in `/etc/resolv.conf` file. The a loopback address such as `127.0.0.1` or `127.0.1.1` and adds this entry to
NetworkManager also sets up `dnsmasq` to use the real DNS servers of the `/etc/resolv.conf`. The `dnsmasq` service provides a local DNS cache to speed up
connection and sets up `nameserver 127.0.0.1` in /`etc/resolv.conf`. DNS look-ups and also provides DHCP services. This configuration will not work
within a Docker container which has its own network namespace. This is because
the Docker container resolves loopback addresses such as `127.0.0.1` to itself,
and it is very unlikely to be running a DNS server on its own loopback address.
When starting containers on desktop machines with these configurations, Docker If Docker detects that no DNS server referenced in `/etc/resolv.conf` is a fully
users see this warning: functional DNS server, the following warning occurs and Docker uses the public
DNS servers provided by Google at `8.8.8.8` and `8.8.4.4` for DNS resolution.
WARNING: Local (127.0.0.1) DNS resolver found in resolv.conf and containers ```none
can't use it. Using default external servers : [8.8.8.8 8.8.4.4] WARNING: Local (127.0.0.1) DNS resolver found in resolv.conf and containers
can't use it. Using default external servers : [8.8.8.8 8.8.4.4]
```
The warning occurs because Docker containers can't use the local DNS nameserver. If you don't use `dnsmasq` or NetworkManaager or have never seen this warning,
Instead, Docker defaults to using an external nameserver. you can skip the rest of this section. To see if you use `dnsmasq`, use the
following command:
To avoid this warning, you can specify a DNS server for use by Docker ```bash
containers. Or, you can disable `dnsmasq` in NetworkManager. Though, disabling $ ps aux |grep dnsmasq
`dnsmasq` might make DNS resolution slower on some networks. ```
The instructions below describe how to configure the Docker daemon If this warning occurs and cannot use the public nameservers, such as when you
running on Ubuntu 14.10 or below. Ubuntu 15.04 and above use `systemd` run a DNS server which resolves hostnames on your internal network, you have
as the boot and service manager. Refer to [control and configure Docker two choices:
with systemd](../../admin/systemd.md#custom-docker-daemon-options) to
configure a daemon controlled by `systemd`.
To specify a DNS server for use by Docker: - You can specify a DNS server for Docker to use.
- You can disable `dnsmasq` in NetworkManager. If you do this, NetworkManager
will add your true DNS nameserver to `/etc/resolv.conf`, but you will lose the
possible benefits of `dnsmasq`.
1. Log into Ubuntu as a user with `sudo` privileges. **You only need to use one of these methods.**
2. Open the `/etc/default/docker` file for editing. #### Specify DNS servers for Docker
$ sudo nano /etc/default/docker The instructions below work whether your Ubuntu installation uses `upstart` or
`systemd`.
3. Add a setting for Docker. The default location of the configuration file is `/etc/docker/daemon.json`. You
can change the location of the configuration file using the `--config-file`
daemon flag. The documentation below assumes the configuration file is located
at `/etc/docker/daemon.json`.
DOCKER_OPTS="--dns 8.8.8.8" 1. Log into Ubuntu as a user with `sudo` privileges.
Replace `8.8.8.8` with a local DNS server such as `192.168.1.1`. You can also 2. Create or edit the Docker daemon configuration file, which defaults to
specify multiple DNS servers. Separated them with spaces, for example: `/etc/docker/daemon.json` file, which controls the Docker daemon
configuration.
--dns 8.8.8.8 --dns 192.168.1.1 ```bash
sudo nano /etc/docker/daemon.json
```
>**Warning**: If you're doing this on a laptop which connects to various 2. Add a `dns` key with one or more IP addresses as values. If the file has
>networks, make sure to choose a public DNS server. existing contents, you only need to add or edit the `dns` line.
```json
{
"dns": ["8.8.8.8", "8.8.4.4"]
}
```
4. Save and close the file. If your internal DNS server cannot resolve public IP addresses, include at
least one DNS server which can, so that you can connect to Docker Hub and so
that your containers can resolve internet domain names.
5. Restart the Docker daemon. Save and close the file.
$ sudo service docker restart 3. Restart the Docker daemon.
```bash
$ sudo service docker restart
```
&nbsp; 4. Verify that Docker can resolve external IP addresses by trying to pull an
&nbsp; image:
**Or, as an alternative to the previous procedure,** disable `dnsmasq` in ```bash
NetworkManager (this might slow your network). $ docker pull hello-world
```
1. Open the `/etc/NetworkManager/NetworkManager.conf` file for editing. 5. If necessary, verify that Docker containers can resolve an internal hostname
by pinging it.
$ sudo nano /etc/NetworkManager/NetworkManager.conf ```bash
$ docker run --rm -it alpine ping -c4 my_internal_host
2. Comment out the `dns=dnsmasq` line: PING google.com (192.168.1.2): 56 data bytes
64 bytes from 192.168.1.2: seq=0 ttl=41 time=7.597 ms
64 bytes from 192.168.1.2: seq=1 ttl=41 time=7.635 ms
64 bytes from 192.168.1.2: seq=2 ttl=41 time=7.660 ms
64 bytes from 192.168.1.2: seq=3 ttl=41 time=7.677 ms
```
dns=dnsmasq #### Disable `dnsmasq` in NetworkManager
3. Save and close the file. If you prefer not to change the Docker daemon's configuration to use a specific
IP address, follow these instructions to disable `dnsmasq` in NetworkManager.
4. Restart both the NetworkManager and Docker. 1. Edit the `/etc/NetworkManager/NetworkManager.conf` file.
$ sudo restart network-manager 2. Comment out the `dns=dnsmasq` line by adding a `#` character to the beginning
$ sudo restart docker of the line.
```none
# dns=dnsmasq
```
Save and close the file.
4. Restart both NetworkManager and Docker. As an alternative, you can reboot
your system.
```bash
$ sudo restart network-manager
$ sudo restart docker
```
### Configure Docker to start on boot ### Configure Docker to start on boot
Ubuntu uses `systemd` as its boot and service manager `15.04` onwards and `upstart` Ubuntu uses `systemd` as its boot and service manager `15.04` onwards and `upstart`
for versions `14.10` and below. for versions `14.10` and below.
For `15.04` and up, to configure the `docker` daemon to start on boot, run #### `systemd`
$ sudo systemctl enable docker ```bash
$ sudo systemctl enable docker
```
For `14.10` and below the above installation method automatically configures `upstart` #### `upstart`
to start the docker daemon on boot
For `14.10` and below, Docker is automatically configured to start on boot using
`upstart`.
## Upgrade Docker ## Upgrade Docker
To install the latest version of Docker with `apt-get`: To install the latest version of Docker with `apt-get`. The following example
fetches information about available versions of all system packages, then
updates Docker if a new version is available.
$ sudo apt-get upgrade docker-engine ```bash
$ sudo apt-get update
$ sudo apt-get upgrade docker-engine
```
## Uninstallation ## Uninstallation
To uninstall the Docker package: To uninstall the Docker package:
$ sudo apt-get purge docker-engine ```bash
$ sudo apt-get purge docker-engine
```
To uninstall the Docker package and dependencies that are no longer needed: To uninstall the Docker package and dependencies that are no longer needed:
$ sudo apt-get autoremove --purge docker-engine ```bash
$ sudo apt-get autoremove --purge docker-engine
```
The above commands will not remove images, containers, volumes, or user created Images, containers, volumes, or customized configuration files on your host are
configuration files on your host. If you wish to delete all images, containers, not automatically removed. To delete all images, containers, and volumes run the
and volumes run the following command: following command:
$ rm -rf /var/lib/docker ```bash
$ rm -rf /var/lib/docker
```
You must delete the user created configuration files manually. You must delete any customized configuration files manually.