by admin
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 imagesREPOSITORY TAG IMAGE ID CREATED SIZEfedora latest 422dc563ca32 2 days ago 252MBubuntu latest dd6f76d9cc90 13 days ago 122MBhello-world latest 725dcfab7d63 13 days ago 1.84kBcentos latest d123f4e55e12 13 days ago 197MB
2. Start one of the docker images.
# docker run -it -d 422dc563ca32 /bin/bash52249ba75f0fa33f93202f4a2d7f83bc71600b8b75ea4db0bc5b56022bf254b6
3. Verify the new Docker container is running.
# docker psCONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES52249ba75f0f 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 }}' 52249ba75f0f172.17.0.2# docker inspect --format='{{ .NetworkSettings.Gateway }}' 52249ba75f0f172.17.0.1Getting 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 -aeth0: 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 0lo: 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 -nKernel IP routing tableDestination Gateway Genmask Flags Metric Ref Use Iface0.0.0.0 172.17.0.1 0.0.0.0 UG 0 0 0 eth0172.17.0.0 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.
