Docker Network working principle detailed _docker

Docker Network Working principle

When the Docker server is Docker daemon starts, it automatically creates a bridge with a name of Docker0, and whenever Docker creates a container, it creates a veth* port on the host named Ethernet. and add this eth* to Docker0 Bridge, in the container will automatically create a name is eth0 Ethernet port, this eth0 and veth* will form a similar pipe to the pair, the corresponding.

Configuring DNS

Docker how to allocate each container hostname and DNS configuration, you can see something by the Mount command in contain:

Mount

...
/DEV/DISK/BY-UUID/5F3D0920-98A8-434A-9C02-8163DCCF6C62 on/etc/resolv.conf type EXT4 (Rw,relatime,errors=remount-ro , data=ordered)
/dev/disk/by-uuid/5f3d0920-98a8-434a-9c02-8163dccf6c62 on/etc/hostname type Ext4 (Rw,relatime, errors=remount-ro,data=ordered)
/dev/disk/by-uuid/5f3d0920-98a8-434a-9c02-8163dccf6c62 on/etc/hosts type Ext4 (rw,relatime,errors=remount-ro,data=ordered)
...

Docker Run's-H can configure container hostname, which can be configured via-h hostname or--hostname=hostname, Docker writes hostname to/etc/hostname

For example:

xiaogang@ubuntu:~/shadowsocks$ sudo docker run-t-i--hostname Ubuu--rm

root@ubuu:/# Cat/etc/hostname
Ubuu

--link=conntainer_nameorid:alias, this option will add an alias to the/etc/hosts, point to Container_nameorid, without knowing the specific IP address, you can use the alias directly instead.

For example:

--dns=ip_address, a ip_address is added to the/ETC/RESOLV.CONF Server tab

--dns-search=domain, it'll be in/etc/. Resolv.conf's Search tab adds a domain, and if a example.com is added to the Search tab, host.example.com is also searched when container needs to find a host's IP.

The/etc/resolv.conf in the container is a copy of the/etc/resolv.conf from the host, except that the local nameserver of the host is filtered out, and if there is no nameserver after filtering, Docker will add Google's public nameserver,8.8.8.8 and 8.8.4.4 to Namerserver. Container modifications are notified when the host is resolv.conf modified

Communication between the container and the container and the outside

1. Need to set Ip_forward system parameters, must be set to 1

$ sysctl net.ipv4.conf.all.forwarding
net.ipv4.conf.all.forwarding = 0
$ sysctl net.ipv4.conf.all.forwarding =1
$ sysctl net.ipv4.conf.all.forwarding
net.ipv4.conf.all.forwarding = 1

2. Need to set up iptables to allow communication between them

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