# 在Gentoo安装Docker

在Gentoo Linux上安装Docker有两种方式：

* 使用官方源
* 使用`docker-overlay`方法

> 官方源由[Gentoo Docker](https://wiki.gentoo.org/wiki/Project:Docker)团队维护
>
> 建议使用官方源的稳定版本`app-emulation/docker`
>
> 如果需要使用`-bin` ebuild，以及实时更新ebuild或者希望使用最新的ebuild，则可以是使用overlay。通过`app-portage/layman`添加`docker-overlay`就可以使用最新且及时更新的文档。

## 可用的USE flags

| USE Flag        | 默认  | 描述                                                     |
| --------------- | --- | ------------------------------------------------------ |
| `aufs`          |     | 通过补丁方式安装`sys-kernel/aufs-sources`，且要激活`CONFIG_AUFS_FS` |
| `btrfs`         |     | 使用btrfs作为存储后端                                          |
| `contrib`       | Yes | 安装附加的脚本和组件                                             |
| `device-mapper` | Yes | 使用`devicemapper`作为存储后端，也就是使用LVM卷管理                     |

> 默认使用`devicemapper`作为存储，请参考"在Gentoo上使用LVM"
>
> USE flags参数描述参考[tianon’s blog](https://tianon.github.io/post/2014/05/17/docker-on-gentoo.html)

## 内核配置

[Docker支持的内核配置参考](https://wiki.gentoo.org/wiki/Docker)

```
General setup  --->
    [*] POSIX Message Queues
    [*] Control Group support  --->
        [*]   Freezer cgroup subsystem
        [*]   Device controller for cgroups
        [*]   Cpuset support
        [*]   Simple CPU accounting cgroup subsystem
        [*]   HugeTLB Resource Controller for Control Groups
        [*]   Enable perf_event per-cpu per-container group (cgroup) monitoring
        [*]   Group CPU scheduler  --->
            [*]   Group scheduling for SCHED_OTHER
            [*]     CPU bandwidth provisioning for FAIR_GROUP_SCHED
    -*- Namespaces support
        [*]   UTS namespace
        [*]   IPC namespace
        [*]   PID Namespaces
        [*]   Network namespace
[*] Networking support  --->
       Networking options  --->
        [*] Network packet filtering framework (Netfilter)  --->
            [*]   Advanced netfilter configuration
            [*]     Bridged IP/ARP packets filtering
         Core Netfilter Configuration  --->
                  *** Xtables matches ***
            <*>   "addrtype" address type match support
            <*>   "conntrack" connection tracking match support
         IP: Netfilter Configuration  --->
            <*> IPv4 connection tracking support (required for NAT)
            <*> IP tables support (required for filtering/masq/NAT)
            <*>   Packet filtering
            <*>   IPv4 NAT
            <*>     MASQUERADE target support
        <*> 802.1d Ethernet Bridging
        [*] QoS and/or fair queueing  --->
            <M>   Control Group Classifier
        [*] Network priority cgroup
Device Drivers  --->
    [*] Multiple devices driver support (RAID and LVM)  --->
        <*>   Device mapper support
        <*>     Thin provisioning target
    [*] Network device support  --->
        [*]   Network core driver support
        <*>     MAC-VLAN support
        <*>     Virtual ethernet pair device
       Character devices  --->
        -*- Enable TTY
        -*-   Unix98 PTY support
        [*]     Support multiple instances of devpts
```

**注意：在`emerge app-emulation/docker`会提示内核参数是否满足要求**

* CONFIG\_MACVLAN
* CONFIG\_VETH
* CONFIG\_BRIDGE
* CONFIG\_BRIDGE\_NETFILTER
* CONFIG\_CGROUP\_HUGETLB
* CONFIG\_NET\_CLS\_CGROUP
* CONFIG\_CFS\_BANDWIDTH （可选，用于容器状态数据搜集）
* CONFIG\_RT\_GROUP\_SCHED
* CONFIG\_CGROUP\_NET\_PRIO
* CONFIG\_BLK\_DEV\_DM
* CONFIG\_DM\_THIN\_PROVISIONING

> 有关内核参数参考 [Docker内核支持参数说明](/cloud-atlas-draft/virtual/docker/engine/an-zhuang/deploy_docker_in_gentoo/docker_kernel.md)

## 编译安装Docker

```bash
emerge --ask app-emulation/docker
```

## 启动Docker

确保内核已经包含了必要的模块和配置（如可选的的`device-mapper`，`AUFS`或`Btrfs`）

要使用Docker，需要以 **root** 身份运行`docker`服务。要以 **non-root** 用户身份运行Docker，则需要使用如下命令将自己加入到`docker`组

```bash
sudo usermod -a -G docker USER
```

### OpenRC

如果使用OpenRC管理启动服务，则使用如下命令启动`docker` deamon

```bash
sudo /etc/init.d/docker start
```

并设置系统启动时启动`docker`

```bash
sudo rc-update add docker
```

### systemd

使用`systemd`管理服务，则使用如下命令

```bash
sudo systemctl start docker
```

设置启动时启动

```bash
sudo systemctl enable docker
```

启动后检查服务进程 `ps aux | grep docker` 可以看到如下进程

```bash
root      1914  2.2  0.8 328408 31220 ?        Ssl  22:26   0:00 /usr/bin/docker daemon -H fd://
```

## 卸载docker

Gentoo Linux卸载docker

```bash
sudo emerge -cav app-emulation/docker
```

要完整卸载Docker软件包和相关不再需要的依赖软件包

```bash
sudo emerge -C app-emulation/docker
```

上述命令不会删除映像、容器、卷或者用户创建的配置文件。如果需要删除所有的映像、容器和卷，可以使用如下命令

```bash
rm -rf /var/lib/docker
```

## 参考

* [Docker Docs - Installation on Gentoo](https://docs.docker.com/engine/installation/linux/gentoolinux/)
* [Gentoo Linux wiki: Docker](https://wiki.gentoo.org/wiki/Docker)


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