11. DevOps: How to Launch a container as a daemon ?

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In continuation of my previous blog on “10. DevOps: How to Build images from Docker containers?”, I am continuing my lab exercises. In this session we can see ”

How to Launch a container as a daemon ?:

Note: If you want to recollect the docker commands to be used during your current lab practice, visit my blog link:

https://vskumarblogs.wordpress.com/2017/12/13/some-useful-docker-commands-for-handling-images-and-containers/

 

Let us recap the past exercises; So far we have experimented with an interactive container, tracked the changes that were made to the containers., created images from the containers, and then gained insights in the containerization scenarios.

Now, let us see the container usage in a detached mode.

When we run the container in a detached mode it runs under a daemon process.

I want to use the “ubuntu” image and run detached mode command.

First, let me check my current docker images:

==================>

vskumar@ubuntu:~$

vskumar@ubuntu:~$ sudo docker images

[sudo] password for vskumar:

REPOSITORY TAG IMAGE ID CREATED SIZE

docker-exercise/ubuntu-wgetinstall latest e34304119838 7 days ago 169MB

<none> <none> fc7e4564eb92 7 days ago 169MB

hello-world latest f2a91732366c 12 days ago 1.85kB

ubuntu 16.04 20c44cd7596f 2 weeks ago 123MB

ubuntu latest 20c44cd7596f 2 weeks ago 123MB

busybox latest 6ad733544a63 4 weeks ago 1.13MB

busybox 1.24 47bcc53f74dc 20 months ago 1.11MB

vskumar@ubuntu:~$

===================>

You can see my previous image with ‘docker-exercise/ubuntu-wgetinstall ‘. This was created in the previous exercise.

As per our plan in this session I am using the below commands to run the ubuntu image as below:

sudo docker run -d ubuntu \

    /bin/bash -c "while true; do date; sleep 5; done";

========== Output ======>
vskumar@ubuntu:~$  sudo docker run -d ubuntu \
>     /bin/bash -c "while true; do date; sleep 5; done";
0fe495fc93edee3aaadc7fc0fbf21997f0ca3cde4d7e563aa8c61352a43957dd
vskumar@ubuntu:~$ $ 
=======================>

Now, to view the docker logs I want to run the docker logs subcommand on image id: ‘ 0fe495fc93edee3aaadc7fc0fbf21997f0ca3cde4d7e563aa8c61352a43957dd’

$ sudo docker logs 0fe495fc93edee3aaadc7fc0fbf21997f0ca3cde4d7e563aa8c61352a43957dd;

=====See the output of the Daemon process running with the ubuntu image ===============>

vskumar@ubuntu:~$ sudo docker logs 0fe495fc93edee3aaadc7fc0fbf21997f0ca3cde4d7e563aa8c61352a43957dd;

Sun Dec 3 05:11:57 UTC 2017

Sun Dec 3 05:12:02 UTC 2017

Sun Dec 3 05:12:07 UTC 2017

Sun Dec 3 05:12:12 UTC 2017

Sun Dec 3 05:12:17 UTC 2017

Sun Dec 3 05:12:22 UTC 2017

Sun Dec 3 05:12:27 UTC 2017

Sun Dec 3 05:12:32 UTC 2017

Sun Dec 3 05:12:37 UTC 2017

Sun Dec 3 05:12:42 UTC 2017

Sun Dec 3 05:12:48 UTC 2017

Sun Dec 3 05:12:53 UTC 2017

Sun Dec 3 05:12:58 UTC 2017

Sun Dec 3 05:13:03 UTC 2017

Sun Dec 3 05:13:08 UTC 2017

Sun Dec 3 05:13:13 UTC 2017

Sun Dec 3 05:13:18 UTC 2017

Sun Dec 3 05:13:23 UTC 2017

Sun Dec 3 05:13:28 UTC 2017

Sun Dec 3 05:13:33 UTC 2017

Sun Dec 3 05:13:38 UTC 2017

Sun Dec 3 05:13:43 UTC 2017

Sun Dec 3 05:13:48 UTC 2017

Sun Dec 3 05:13:53 UTC 2017

Sun Dec 3 05:13:58 UTC 2017

Sun Dec 3 05:14:03 UTC 2017

Sun Dec 3 05:14:08 UTC 2017

Sun Dec 3 05:14:13 UTC 2017

Sun Dec 3 05:14:18 UTC 2017

Sun Dec 3 05:14:23 UTC 2017

Sun Dec 3 05:14:28 UTC 2017

Sun Dec 3 05:14:33 UTC 2017

Sun Dec 3 05:14:38 UTC 2017

Sun Dec 3 05:14:43 UTC 2017

Sun Dec 3 05:14:48 UTC 2017

Sun Dec 3 05:14:53 UTC 2017

Sun Dec 3 05:14:58 UTC 2017

Sun Dec 3 05:15:03 UTC 2017

Sun Dec 3 05:15:08 UTC 2017

Sun Dec 3 05:15:13 UTC 2017

Sun Dec 3 05:15:18 UTC 2017

Sun Dec 3 05:15:23 UTC 2017

vskumar@ubuntu:~$

=================You can see the output for every few seconds listed =======>

It means the container is running as a daemon.

Now, let us use ps -eaf command to check the processed running in linux by using :

$ ps -eaf | grep ‘daemon’

========= See the output of daemon processes ==========>

vskumar@ubuntu:~$

vskumar@ubuntu:~$ ps -eaf | grep ‘daemon’

message+ 837 1 0 20:26 ? 00:00:05 /usr/bin/dbus-daemon –system –address=systemd: –nofork –nopidfile –systemd-activation

root 871 1 0 20:26 ? 00:00:03 /usr/sbin/NetworkManager –no-daemon

avahi 873 1 0 20:26 ? 00:00:00 avahi-daemon: running [ubuntu.local]

root 876 1 0 20:26 ? 00:00:01 /usr/lib/accountsservice/accounts-daemon

avahi 893 873 0 20:26 ? 00:00:00 avahi-daemon: chroot helper

rtkit 1370 1 0 20:28 ? 00:00:00 /usr/lib/rtkit/rtkit-daemon

vskumar 2426 1 0 20:55 ? 00:00:00 /usr/bin/gnome-keyring-daemon –daemonize –login

vskumar 2508 2428 0 20:55 ? 00:00:00 upstart-udev-bridge –daemon –user

vskumar 2515 2428 0 20:55 ? 00:00:04 dbus-daemon –fork –session –address=unix:abstract=/tmp/dbus-nPaV5rWlQc

vskumar 2570 2428 0 20:55 ? 00:00:03 /usr/lib/x86_64-linux-gnu/bamf/bamfdaemon

vskumar 2572 2428 0 20:55 ? 00:00:04 /usr/bin/ibus-daemon –daemonize –xim –address unix:tmpdir=/tmp/ibus

vskumar 2575 2428 0 20:55 ? 00:00:00 upstart-file-bridge –daemon –user

vskumar 2579 2428 0 20:55 ? 00:00:00 upstart-dbus-bridge –daemon –system –user –bus-name system

vskumar 2582 2428 0 20:55 ? 00:00:00 upstart-dbus-bridge –daemon –session –user –bus-name session

vskumar 2605 2428 0 20:55 ? 00:00:00 /usr/lib/ibus/ibus-x11 –kill-daemon

vskumar 2630 2428 0 20:56 ? 00:00:00 gpg-agent –homedir /home/vskumar/.gnupg –use-standard-socket –daemon

vskumar 2645 2428 0 20:56 ? 00:00:02 /usr/lib/unity-settings-daemon/unity-settings-daemon

vskumar 2664 2653 0 20:56 ? 00:00:00 /usr/bin/dbus-daemon –config-file=/etc/at-spi2/accessibility.conf –nofork –print-address 3

vskumar 2851 2654 0 20:56 ? 00:00:01 /usr/lib/unity-settings-daemon/unity-fallback-mount-helper

vskumar 2914 2428 0 20:57 ? 00:00:00 /bin/sh -c /usr/lib/x86_64-linux-gnu/zeitgeist/zeitgeist-maybe-vacuum; /usr/bin/zeitgeist-daemon

vskumar 2920 2914 0 20:57 ? 00:00:00 /usr/bin/zeitgeist-daemon

vskumar 3094 2428 0 21:00 ? 00:00:01 /usr/lib/x86_64-linux-gnu/unity-lens-files/unity-files-daemon

root 4148 1253 0 21:11 ? 00:00:00 docker-containerd-shim –namespace moby –workdir /var/lib/docker/containerd/daemon/io.containerd.runtime.v1.linux/moby/0fe495fc93edee3aaadc7fc0fbf21997f0ca3cde4d7e563aa8c61352a43957dd –address /var/run/docker/containerd/docker-containerd.sock –runtime-root /var/run/docker/runtime-runc

vskumar 4480 3206 0 21:19 pts/19 00:00:00 grep –color=auto daemon

vskumar@ubuntu:~$

======== You can see the list of processes running currently ========>

So we are successful! to run a container in a detached mode [not in an interactive mode!] using the command: ‘ sudo docker run -d ubuntu’

You can think in an application architecture having multiple servers or SOA running with different services.

You can simulate the same services using the docker containers, by setting up as images by configuring the required services and connect them to the architecture.

This way the advantages of containers can be utilized well. Where different companies are using and implementing their applications into containers architecture by saving lot of infrastructure cost. No hardware or physical servers are required. Lot of space also can be saved. The microservices architecture leads to the same way.

At this point, I would like to stop this session and in the next blog we will see other exercises.

Vcard-Shanthi Kumar V-v3

 

 

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