Docker实践
作为目前最火热的容器技术，docker在网络实现和管理方面还存在不足。最开始的docker是依赖于Linux Bridge实现的网络设置，只能在容器里创建一个网卡。后来随着docker/libnetwork项目的进展，docker的网络管理功能逐渐多了起来。尽管如此，跨主机通信对于docker来说还是一个需要面对的问题，这一点对于kubernetes类的容器管理系统异常重要。目前市面上主流的解决方法有flannel, weave, Pipework, Open vSwitch等。Open vSwitch实现比较简单，成熟且功能强大，所以很适合作为解决docker底层网络互联互通的工具。言归正传，如下是基本架构图：
http://s1.运维网.com/images/20180201/1517468962735163.png
具体的实现步骤如下：
1. 安装docker, bridge-utils和openvswitch
# yum install docker bridge-utils -y
# yum install wget openssl-devel -y
# yum groupinstall "Development Tools"
# adduser ovswitch
# su - ovswitch
$ wget http://openvswitch.org/releases/openvswitch-2.3.0.tar.gz
$ tar -zxvpf openvswitch-2.3.0.tar.gz
$ mkdir -p ~/rpmbuild/SOURCES
$ sed 's/openvswitch-kmod, //g' openvswitch-2.3.0/rhel/openvswitch.spec > openvswitch-2.3.0/rhel/openvswitch_no_kmod.spec
$ cp openvswitch-2.3.0.tar.gz rpmbuild/SOURCES/
$ rpmbuild -bb --without check ~/openvswitch-2.3.0/rhel/openvswitch_no_kmod.spec
$ exit
# yum localinstall /home/ovswitch/rpmbuild/RPMS/x86_64/openvswitch-2.3.0-1.x86_64.rpm -y
# mkdir /etc/openvswitch
# setenforce 0 2. 在dockerserver1上编辑/usr/lib/systemd/system/docker.service文件，添加docker启动选项"--bip=10.0.0.1/24"，如下：
# cat /usr/lib/systemd/system/docker.service
Description=Docker Application Container Engine
Documentation=http://docs.docker.com
After=network.target rhel-push-plugin.socket registries.service
Wants=docker-storage-setup.service
Requires=docker-cleanup.timer
Type=notify
NotifyAccess=all
EnvironmentFile=-/run/containers/registries.conf
EnvironmentFile=-/etc/sysconfig/docker
EnvironmentFile=-/etc/sysconfig/docker-storage
EnvironmentFile=-/etc/sysconfig/docker-network
Environment=GOTRACEBACK=crash
Environment=DOCKER_HTTP_HOST_COMPAT=1
Environment=PATH=/usr/libexec/docker:/usr/bin:/usr/sbin
ExecStart=/usr/bin/dockerd-current \
--add-runtime docker-runc=/usr/libexec/docker/docker-runc-current \
--default-runtime=docker-runc \
--exec-opt native.cgroupdriver=systemd \
--userland-proxy-path=/usr/libexec/docker/docker-proxy-current \
--bip=10.0.0.1/24 \
$OPTIONS \
$DOCKER_STORAGE_OPTIONS \
$DOCKER_NETWORK_OPTIONS \
$ADD_REGISTRY \
$BLOCK_REGISTRY \
$INSECURE_REGISTRY\
$REGISTRIES
ExecReload=/bin/kill -s HUP $MAINPID
LimitNOFILE=1048576
LimitNPROC=1048576
LimitCORE=infinity
TimeoutStartSec=0
Restart=on-abnormal
MountFlags=slave
KillMode=process
WantedBy=multi-user.target
# 3. 在dockerserver2上编辑/usr/lib/systemd/system/docker.service文件，添加docker启动选项"--bip=10.0.1.1/24"，如下：
# cat /usr/lib/systemd/system/docker.service
Description=Docker Application Container Engine
Documentation=http://docs.docker.com
After=network.target rhel-push-plugin.socket registries.service
Wants=docker-storage-setup.service
Requires=docker-cleanup.timer
Type=notify
NotifyAccess=all
EnvironmentFile=-/run/containers/registries.conf
EnvironmentFile=-/etc/sysconfig/docker
EnvironmentFile=-/etc/sysconfig/docker-storage
EnvironmentFile=-/etc/sysconfig/docker-network
Environment=GOTRACEBACK=crash
Environment=DOCKER_HTTP_HOST_COMPAT=1
Environment=PATH=/usr/libexec/docker:/usr/bin:/usr/sbin
ExecStart=/usr/bin/dockerd-current \
--add-runtime docker-runc=/usr/libexec/docker/docker-runc-current \
--default-runtime=docker-runc \
--exec-opt native.cgroupdriver=systemd \
--userland-proxy-path=/usr/libexec/docker/docker-proxy-current \
--bip=10.0.1.1/24 \
$OPTIONS \
$DOCKER_STORAGE_OPTIONS \
$DOCKER_NETWORK_OPTIONS \
$ADD_REGISTRY \
$BLOCK_REGISTRY \
$INSECURE_REGISTRY\
$REGISTRIES
ExecReload=/bin/kill -s HUP $MAINPID
LimitNOFILE=1048576
LimitNPROC=1048576
LimitCORE=infinity
TimeoutStartSec=0
Restart=on-abnormal
MountFlags=slave
KillMode=process
WantedBy=multi-user.target
#
4. 在两个主机上启动docker服务
# systemctl start docker
# systemctl enable docker
5. docker服务启动后，可以看到一个新的bridge docker0被创建出来，并且被赋予了我们之前配置的IP地址:
# brctl show
bridge name bridge id STP enabled interfaces
docker0 8000.02427076111e no
# ifconfig docker0
docker0: flags=4099mtu 1500
inet 10.0.0.1netmask 255.255.255.0broadcast 0.0.0.0
ether 02:42:70:76:11:1etxqueuelen 0(Ethernet)
RX packets 0bytes 0 (0.0 B)
RX errors 0dropped 0overruns 0frame 0
TX packets 0bytes 0 (0.0 B)
TX errors 0dropped 0 overruns 0carrier 0collisions 0
## brctl show
bridge name bridge id STP enabled interfaces
docker0 8000.0242ba00c394 no
# ifconfig docker0
docker0: flags=4099mtu 1500
inet 10.0.1.1netmask 255.255.255.0broadcast 0.0.0.0
ether 02:42:ba:00:c3:94txqueuelen 0(Ethernet)
RX packets 0bytes 0 (0.0 B)
RX errors 0dropped 0overruns 0frame 0
TX packets 0bytes 0 (0.0 B)
TX errors 0dropped 0 overruns 0carrier 0collisions 0
#
6. 在两个主机上启动openvswitch
# systemctl start openvswitch
# chkconfig openvswitch on
7. 在两个主机上创建隧道网桥br-tun，并通过VXLAN协议创建隧道
# ovs-vsctl add-br br-tun
# ovs-vsctl add-port br-tun vxlan0 -- set Interface vxlan0 type=vxlan options:remote_ip=10.10.172.204
# brctl show
bridge name bridge id STP enabled interfaces
docker0 8000.02427076111e no br-tun
# ovs-vsctl add-br br-tun
# ovs-vsctl add-port br-tun vxlan0 -- set Interface vxlan0 type=vxlan options:remote_ip=10.10.172.203
# brctl show
bridge name bridge id STP enabled interfaces
docker0 8000.0242ba00c394 no br-tun
8. 将br-tun作为接口加入docker0网桥
# brctl addif docker0 br-tun
# brctl addif docker0 br-tun
9. 由于两个主机的容器处于不同的网段，需要添加路由才能让两边的容器互相通信
# ip route add 10.0.1.0/24 via 10.10.172.204 dev eth0
# ip route add 10.0.0.0/24 via 10.10.172.203 dev eth0
10. 在两个主机上各自启动一个docker容器，验证互相能否通信。
# docker run --rm -it centos /bin/bash
# yum install net-tools -y
# ifconfig eth0
eth0: flags=4163mtu 1500
inet 10.0.0.2netmask 255.255.255.0broadcast 0.0.0.0
inet6 fe80::42:aff:fe00:2prefixlen 64scopeid 0x20
ether 02:42:0a:00:00:02txqueuelen 0(Ethernet)
RX packets 4266bytes 13337782 (12.7 MiB)
RX errors 0dropped 0overruns 0frame 0
TX packets 4144bytes 288723 (281.9 KiB)
TX errors 0dropped 0 overruns 0carrier 0collisions 0
## docker run --rm -it centos /bin/bash
# yum install net-tools -y
# ifconfig eth0
eth0: flags=4163mtu 1500
inet 10.0.1.2netmask 255.255.255.0broadcast 0.0.0.0
inet6 fe80::42:aff:fe00:102prefixlen 64scopeid 0x20
ether 02:42:0a:00:01:02txqueuelen 0(Ethernet)
RX packets 4536bytes 13344451 (12.7 MiB)
RX errors 0dropped 0overruns 0frame 0
TX packets 4381bytes 301685 (294.6 KiB)
TX errors 0dropped 0 overruns 0carrier 0collisions 0
# ping 10.0.0.2
PING 10.0.0.2 (10.0.0.2) 56(84) bytes of data.
64 bytes from 10.0.0.2: icmp_seq=1 ttl=62 time=1.68 ms
^C
--- 10.0.0.2 ping statistics ---
1 packets transmitted, 1 received, 0% packet loss, time 0ms
rtt min/avg/max/mdev = 1.683/1.683/1.683/0.000 ms
# 11.查看两个docker宿主机的网卡信息
# ip addr list
1: lo:mtu 65536 qdisc noqueue state UNKNOWN
link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
inet 127.0.0.1/8 scope host lo
valid_lft forever preferred_lft forever
inet6 ::1/128 scope host
valid_lft forever preferred_lft forever
2: eth0:mtu 1500 qdisc mq state UP qlen 1000
link/ether 00:50:56:86:3e:d8 brd ff:ff:ff:ff:ff:ff
inet 10.10.172.203/24 brd 10.10.172.255 scope global eth0
valid_lft forever preferred_lft forever
inet6 fe80::250:56ff:fe86:3ed8/64 scope link
valid_lft forever preferred_lft forever
3: docker0:mtu 1500 qdisc noqueue state DOWN
link/ether 02:42:70:76:11:1e brd ff:ff:ff:ff:ff:ff
inet 10.0.0.1/24 scope global docker0
valid_lft forever preferred_lft forever
inet6 fe80::42:70ff:fe76:111e/64 scope link
valid_lft forever preferred_lft forever
4: ovs-system:mtu 1500 qdisc noop state DOWN
link/ether 06:19:20:ae:f6:61 brd ff:ff:ff:ff:ff:ff
5: br-tun:mtu 1500 qdisc noop master docker0 state DOWN
link/ether 42:2c:39:7f:a2:4a brd ff:ff:ff:ff:ff:ff
## ip addr
1: lo:mtu 65536 qdisc noqueue state UNKNOWN
link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
inet 127.0.0.1/8 scope host lo
valid_lft forever preferred_lft forever
inet6 ::1/128 scope host
valid_lft forever preferred_lft forever
2: eth0:mtu 1500 qdisc mq state UP qlen 1000
link/ether 00:50:56:86:22:d8 brd ff:ff:ff:ff:ff:ff
inet 10.10.172.204/24 brd 10.10.172.255 scope global eth0
valid_lft forever preferred_lft forever
inet6 fe80::250:56ff:fe86:22d8/64 scope link
valid_lft forever preferred_lft forever
3: docker0:mtu 1500 qdisc noqueue state DOWN
link/ether 02:42:ba:00:c3:94 brd ff:ff:ff:ff:ff:ff
inet 10.0.1.1/24 scope global docker0
valid_lft forever preferred_lft forever
inet6 fe80::42:baff:fe00:c394/64 scope link
valid_lft forever preferred_lft forever
4: ovs-system:mtu 1500 qdisc noop state DOWN
link/ether be:d4:64:ee:cb:29 brd ff:ff:ff:ff:ff:ff
5: br-tun:mtu 1500 qdisc noop master docker0 state DOWN
link/ether 6e:3d:3e:1a:6a:4e brd ff:ff:ff:ff:ff:ff
#
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