Prema – Best DevOps

Define Docker

Prema — Tue, 17 Aug 2021 07:26:06 +0000

Docker is a tool /platform to manage containers
Fast, consistent delivery of your applications
faster deployment and good performance
Docker is light weight
uses less resources
cost saving
time saving
effective infra management

Day:2 Docker Update

Prema — Tue, 17 Aug 2021 05:26:02 +0000

[root@ip-172-31-14-110 centos]# docker update –cpu-shares 512 c04ba627e5ae ecstatic_shaw
d28b65c987d8
ecstatic_shaw
[root@ip-172-31-14-110 centos]# docker diff c04ba627e5ae
C /tmp
A /tmp/jetty-0_0_0_0-8080-war-_-any-8581425030792705993
A /tmp/winstone6787664488571520537.jar
A /tmp/hsperfdata_jenkins
A /tmp/hsperfdata_jenkins/7

wait

docker wait command waits for one or more container to exit and provides the return status of the docker exit

[root@ip-172-31-15-56 centos]# docker wait c04ba627e5ae
0
[root@ip-172-31-15-56 centos]#

[root@ip-172-31-15-56 centos]# docker wait c04ba627e5ae
137
[root@ip-172-31-15-56 centos]#

Day1 Answers

Prema — Mon, 16 Aug 2021 10:24:02 +0000

What is the diff between docker pause and docker unpause?

docker stop: Stop a running container (send SIGTERM, and then SIGKILL after grace period) […] The main process inside the container will receive SIGTERM, and after a grace period, SIGKILL. [emphasis mine]

docker kill: Kill a running container (send SIGKILL, or specified signal) […] The main process inside the container will be sent SIGKILL, or any signal specified with option –signal. [emphasis mine]

The docker unpause command un-suspends all processes in the specified containers. On Linux, it does this using the freezer cgroup.

The docker pause command suspends all processes in the specified containers. On Linux, this uses the freezer cgroup. Traditionally, when suspending a process the SIGSTOP signal is used, which is observable by the process being suspended. With the freezer cgroup the process is unaware, and unable to capture, that it is being suspended, and subsequently resumed. On Windows, only Hyper-V containers can be paused.

Pause basically on a temporary basis stops all specified contains and we can unpause the specified containers with the below command

docker pause
docker unpause

CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
bf3be341680e jenkins/jenkins “/sbin/tini — /usr/…” 14 minutes ago Up 14 minutes 8080/tcp, 50000/tcp quizzical_cannon

What is the diff between docker stop and docker kill?
Docker kill command kills the specified container that container will no longer run any process and shwos as exited
STOP basically stops the specified container with the process and also shows as exited

docker stop
docker kill