[CENTOS] Docker operation memo

usage environment

VirtulBox : 6.1 Host OS: Ubuntu 18.04 Docer : docker-ce 19.03.13

• The host OS of docker is a virtual environment running on VirtualBox.

Image execution

When booting CentOS with privileges.

$ sudo docker run -itd --privileged --name PROCESS_NAME IMAGE_NAME /sbin/init
$ sudo docker run -itd --privileged -p 8080:80 --name PROCESS_NAME IMAGE_NAME /sbin/init
↑ When specifying the port, it looks like this

• Sudo is not required if the user to be executed is included in the docker group.

Checking the status of the container

Stream

$ sudo docker stats centos8

Do not stream

$ sudo docker stats centos8 --no-stream

Set memory limit after booting

I stumbled in various ways, but succeeded by doing the following.

$ sudo docker update -m 1G --memory-swap -1 CONTAINER_ID

The following things such as stumbling

At first, I executed the following command, but an error occurred.

$ sudo docker update -m 1G CONTAINER_ID
Your kernel does not support swap limit capabilities or the cgroup is not mounted. Memory limited without swap.

Solved by changing the swap setting of grub.

$ sudo vi /etc/default/grub
$ sudo update-grub
grub.Update cfg and restart the host OS.

When I re-executed it after restarting, the following error occurred.

$ docker update -m 1G 917f3986a06b
Error response from daemon: Cannot update container 917f3986a06bb9f99b095af4f3e5334ce125f596f9926db2733bdb4d20868b47: Memory limit should be smaller than already set memoryswap limit, update the memoryswap at the same time

So, I set the "--memory-swap -1" option and executed it, and it succeeded.

When the memory is loaded as shown below, it can be confirmed that the 1G limit is applied.

$ docker exec -it centos8 /bin/bash
# /dev/null < `yes`

$ docker stats centos8 --no-stream
CONTAINER ID        NAME                CPU %               MEM USAGE / LIMIT   MEM %               NET I/O             BLOCK I/O           PIDS
917f3986a06b        centos8             106.50%             1GiB / 1GiB         100.00%             15.4kB / 10.4kB     52.3MB / 4.1kB      229