What is docker update and docker wait? Explain with example commands. update : Update configuration of one or more containers docker update f4d703072499 Wait : wait Block until one or more containers stop, then print their exit codes docker wait f4d703072499 CMD ENTRYPOINT Can be overridden Cannot be overridden Cannot append additional params Can be appended Command to run when container starts or arg to ENTRYPOINT if specified Always first command to run when container starts Multiple times can be

5 Differences CMD Entrypoint It can be replaced by commandin docker run Ex:-[root@ip-172-31-17-58 sample3]# docker run -it test-sample1 /bin/bashroot@373fb5615122:/# Although dockerfile had CMD /usr/sbin/apache2ctl -D FOREGROUND If attempted to be replaced via docker run commandit will instead be added as a run time argument to actual entry point commandEx:-[root@ip-172-31-17-58 sample3]# docker run test-sample3 /bin/bashHello /bin/bash where dockerfile had entrypoint as below ENTRYPOINT [“/bin/echo”, “Hello”] CMD will be included as a 2nd command to be executed alongwith Entrypoint For ex –

What about if you 2 CMD? It will remove the intermediate container and take the latest changes. FROM ubuntu MAINTAINER Rajesh Kumar << rajesh@scmgalaxy.com>> ENV DEBIAN_FRONTEND=noninteractive RUN apt-get update RUN apt-get -y install tzdata RUN apt-get install git -y && apt-get install -yq apache2 CMD echo “Hello world” CMD echo “Hi” result: Hi Last CMD will be executed. What about if you 2 ENRTYPOINT? It will remove the intermediate container and take the latest changes. FROM ubuntu MAINTAINER Rajesh Kumar

CMD ENTRYPOINT Can be overridden Cannot be overridden Cannot append additional params Can be appended Command to run when container starts or arg to ENTRYPOINT if specified Always first command to run when container starts Multiple times can be added in the dockerfile but the last line will override the previous Same behavior as CMD Treated as additional param when it is used along with ENTRYPOINT Always the main command

What is docker update and docker wait? Explain with example commands. Docker Update:Update the container configuration like cpu, memory, restart policy, etc. docker update –kernel-memory 512M rameshdocker update –restart=on-failure:3 rameshdocker update –cpus 2 rameshdocker update –restart=no ramesh Docker Wait: Block until one or more containers stop, then print their exit codes. docker wait ramesh127docker ps -a |grep ramesh7181391c7b98 ubuntu “bash” 50 minutes ago Exited (127) 30 seconds agodocker wait ramesh0docker stop rameshdocker wait ramesh137docker kill ramesh prints the exit codes

What is docker update ? We can change the configurations of an already running container which is observed by the docker server for > 10 seconds in the following test which we are going to run using the restart policy. Then went inside the container using bash and killed it using process id 1 Although the container got terminated by itself still due to restart policy came back again One more thing to note is when we did a docker

Block until one or more containers stop, then print their exit codes

Docker update:The docker update command dynamically updates container configuration.You can use this command to prevent containers from consuming too many resources from their Docker host. With a single command, you can place limits on a single container or on many. To specify more than one container, provide space-separated list of container names or IDs Command example:docker update –cpus 4 320f02d6f0f7 Docker waitBlock until one or more containers stop, then print their exit codes Example:1st terminaldocker wait 320f02d6f0f7In another terminal, stop

The docker update command dynamically updates container configuration. You can use this command to prevent containers from consuming too many resources from their Docker host.

It Blocks the docker until one or more containers stop, then prints the respective exit codes

docker update Updates the running/exited container configuration such as memory, cpu, restart, and etc., docker wait Blocks the terminal execution till one or more containers stop and then print their exit codes.

The docker update command dynamically updates container configuration. You can use this command to prevent containers from consuming too many resources from their Docker host. With a single command, you can place limits on a single container or on many. “docker wait” is equivalent to “docker container wait”. Block until one or more containers stop, then print their exit codes means this command would to wait until Docker container stops and print a exit code.

Update : [root@ip-172-31-17-58 centos]# docker update –pids-limit 5 6344a718da9b6344a718da9b[root@ip-172-31-17-58 centos]# docker update –help[root@ip-172-31-17-58 centos]# docker update –cpu-period 200 8d2f95364af1Error response from daemon: CPU cfs period can not be less than 1ms (i.e. 1000) or larger than 1s (i.e. 1000000)[root@ip-172-31-17-58 centos]# docker update –cpu-period 2000 8d2f95364af1 wait : [root@ip-172-31-17-58 centos]# docker start 8d2f95364af18d2f95364af1[root@ip-172-31-17-58 centos]# docker stop 8d2f95364af18d2f95364af1 In another terminal : [root@ip-172-31-17-58 centos]# clear[root@ip-172-31-17-58 centos]# docker wait 8d2f95364af10[root@ip-172-31-17-58 centos]#

Difference between docker kill/stop For docker kill – process exits with a bad status code – 137 For docker stop – process exits with a good status code – 0 That validates what is specified in the documentation that for docker kill – process is terminated unexpectedly whereas for docker stop – process is terminated abruptly. Note for the containers above we had got the status codes post below commands Difference between docker pause/unpause We can apply pause on a

What is diff between docker pause/unpause and stop/kill? Docker Pause will suspend all the process inside a container by sending SIGSTOP command, where as in Docker stop the main process will receive SIGTERM and after a grace period it receives SIGKILL. SIGSTOP is the pause signal. The only behavior is to pause the process; the signal cannot be caught or ignored. The shell uses pausing (and its counterpart, resuming via SIGCONT) to implement job control. SIGTERM is the termination signal.

Pause/Unpause Pause: when the running container is paused “SIGSTOP”is processed inside the container and become paused state. (Freeze CGroup)Unpause: Unpause execute “SIGCONT” inside the container to restore the container process (UnFreeze CGroup) Stop/Kill Stop: Stop execute “SIGTERM” inside the container and stop the process and the container and once grace period exceeded still stopping state then “SIGKILL” will executed (Gracefully stops) Kill: Kill execute “SIGKILL” inside the container and stops immediately or specified –signal will be executed (Terminates abruptly)

Docker pause : pauses all processes within one or more containers. Docker unpause : unpauses all processes within one or more containers Docker stop : Stop one or more running containers Docker kill : Kill one or more running containers

The docker pause command suspends all processes in the specified containers. On Linux, this uses the cgroups freezer. Traditionally, when suspending a process the SIGSTOP signal is used, which is observable by the process being suspended The docker stop command. The main process inside the container will receive SIGTERM, and after a grace period, SIGKILL. SIGTERM is the termination signal. The default behavior is to terminate the process, but it also can be caught or ignored. The intention is to

Kill/stop Kill -unsafe exit stop- safe exit pause/unpause

Containerization is motivated by need of dynamic scaling and resource allocation. Docker allows us to work in different environments and share with different involved stakeholders with ease.