Here is a short note on how to pull information of the container running on the host. This is similar to the “xm list –long [domain_ID]” command in xen.
Getting information from outside of the Docker Container
1. Below are the list of images that are residing on the host node.
# docker images REPOSITORY TAG IMAGE ID CREATED SIZE fedora latest 422dc563ca32 2 days ago 252MB ubuntu latest dd6f76d9cc90 13 days ago 122MB hello-world latest 725dcfab7d63 13 days ago 1.84kB centos latest d123f4e55e12 13 days ago 197MB
2. Start one of the docker images.
# docker run -it -d 422dc563ca32 /bin/bash 52249ba75f0fa33f93202f4a2d7f83bc71600b8b75ea4db0bc5b56022bf254b6
3. Verify the new Docker container is running.
# docker ps CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES 52249ba75f0f 422dc563ca32 "/bin/bash" About a minute ago Up About a minute gracious_keller
The “inspect“” command will list the complete information of the container. Use the container ID listed in the first column with the inspect option. You will get a pretty long output here.
# docker inspect 52249ba75f0f
[
{
"Id": "52249ba75f0fa33f93202f4a2d7f83bc71600b8b75ea4db0bc5b56022bf254b6",
"Created": "2017-11-17T14:38:05.340313315Z",
"Path": "/bin/bash",
"Args": [],
"State": {
"Status": "running",
"Running": true,
"Paused": false,
"Restarting": false,
"OOMKilled": false,
"Dead": false,
"Pid": 1535,
"ExitCode": 0,
"Error": "",
"StartedAt": "2017-11-17T14:38:05.638951265Z",
"FinishedAt": "0001-01-01T00:00:00Z"
}
.......
4. This can also be truncated based on what needs to be verified. For example, you could only get information on the networking part of the Docker Container.
# docker inspect --format='{{ .NetworkSettings.IPAddress }}' 52249ba75f0f
172.17.0.2
# docker inspect --format='{{ .NetworkSettings.Gateway }}' 52249ba75f0f
172.17.0.1
Getting Information from inside the Docker Container
The below example is to show the settings from inside the Docker container.
1. First, attach to the docker container.
# docker attach 52249ba75f0f
2. When you attach to a brand new container, commands like ifconfig, route will not work. As the docker is a bare minimal installation and we have to install the packages as and when they are required. So, to run ifconfig and route command, first install the net-tools package.
# yum install net-tools
3. Now run the commands ifconfig and route to get the required information about the Docker container.
# ifconfig -a
eth0: flags=4163[UP,BROADCAST,RUNNING,MULTICAST] mtu 1500
inet 172.17.0.2 netmask 255.255.0.0 broadcast 0.0.0.0
ether 02:42:ac:11:00:02 txqueuelen 0 (Ethernet)
RX packets 36502 bytes 72894961 (69.5 MiB)
RX errors 0 dropped 0 overruns 0 frame 0
TX packets 22286 bytes 1594850 (1.5 MiB)
TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0
lo: flags=73[UP,LOOPBACK,RUNNING] mtu 65536
inet 127.0.0.1 netmask 255.0.0.0
loop txqueuelen 1 (Local Loopback)
RX packets 0 bytes 0 (0.0 B)
RX errors 0 dropped 0 overruns 0 frame 0
TX packets 0 bytes 0 (0.0 B)
TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0
# route -n Kernel IP routing table Destination Gateway Genmask Flags Metric Ref Use Iface 0.0.0.0 172.17.0.1 0.0.0.0 UG 0 0 0 eth0 172.17.0.0 0.0.0.0 255.255.0.0 U 0 0 0 eth0
Container config file
Also, the information about the container will be stored as config file and can be used to re-initiate the container. The path location for the container can be collected from the earlier “inspect” command.