The Docker platform leverages Docker containers to enable IT operations teams and Developer teams to build, ship and run any application, anywhere. (from docker.com)
I’ve been working with Docker for 3 years now and seen some cases where an image has to perform some steps before booting the application(s). It’s usual to see that done with a bash script that doesn’t launch the application preceded by an exec command. Let me explain:
Lately I’ve been working with Docker experimenting development setups with JBoss Wildfly, ActiveMQ, Jenkins, Postfix, Nagios, etc. For those who are not familiar with:
Docker is an open platform for developers and sysadmins to build, ship, and run distributed applications.
You can easily create a container with your ideal setup and deploy your app, in a matter of minutes! You can have fun with Docker, here.
Nagios is a very powerful monitoring tool that can help you to monitor your infrastructure, detect security breaches, spot problems before they occur, etc.
I’ve forked Brian Goff Nagios image and added the possibility to monitor HTTPS by enabling SSL (here). But then, how do I create my configuration files and add them to Nagios?
Based on cpuguy83 Nagios or my image, I’ve created the following Dockerfile:
# Nagios docker modified image # VERSION 1.0 # use tpires/nagios base image (SSL ON) FROM tpires/nagios MAINTAINER Tiago Pires, tandrepires@gmail.com # Install/remove dependencies ENV DEBIAN_FRONTEND noninteractive # I've had some troubles trying to configure postfix inside nagios, so let's remove it and later create a postfix image to also be used by other containers. RUN apt-get remove -y --purge postfix RUN apt-get install -y msmtp heirloom-mailx RUN apt-get autoremove -y RUN apt-get autoclean ADD launch.sh /launch.sh RUN chmod +x /launch.sh EXPOSE 80 CMD ["/bin/bash", "-c", "/launch.sh"]
(I’m going to use an external postfix image to send emails. You can, of course, keep and configure postfix inside this image.)
We’re adding an init script launch.sh, to let us copy configuration file(s) to our Nagios image and edit some of the existing ones. But where will those configuration file(s) come from? Later, we’ll create a nagios configuration image containing them. Let’s have a look at launch.sh first.
#!/bin/bash # If $NAGIOS HOME isn't set, set it! if [ -z $NAGIOS_HOME ]; then NAGIOS_HOME=/opt/nagios fi # Create, if not already, servers configuration directory if [ ! -d "$NAGIOS_HOME/etc/servers" ]; then mkdir -p $NAGIOS_HOME/etc/servers fi # Copy all existing configuration file(s) to Nagios servers directory and uncomment that line in nagios.cfg. if [ ! -z $CONF_PATH ]; then cp -f $CONF_PATH/*.cfg $NAGIOS_HOME/etc/servers/ sed -i "s|#cfg_dir=$NAGIOS_HOME/etc/servers|cfg_dir=$NAGIOS_HOME/etc/servers|g" $NAGIOS_HOME/etc/nagios.cfg fi # mail configuration # We're setting MSMTP client to connect to our postfix and send emails. # If you're using an external postfix image don't forget to set an environment variable MAIL. if [ ! -z /etc/msmtprc ]; then echo 'account postfix' > /etc/msmtprc echo 'host postfix' >> /etc/msmtprc echo 'port 25' >> /etc/msmtprc echo 'from '$POSTFIX_ENV_MAIL >> /etc/msmtprc echo 'protocol smtp' >> /etc/msmtprc echo 'account default : postfix' >> /etc/msmtprc chmod 600 /etc/msmtprc cp /etc/msmtprc $NAGIOS_HOME/.msmtprc chown nagios:nagios $NAGIOS_HOME/.msmtprc # remove postfix from the startup script rm -rf /etc/sv/postfix fi # Modify system default client to msmtp. if [ ! -z /etc/mailrc ]; then echo 'set sendmail=/usr/bin/msmtp' > /etc/mailrc echo 'set sendmail=/usr/bin/msmtp' >> /etc/nail.rc echo 'set smtp=postfix:25' >> /etc/nail.rc ## i'm using postfix as host due to --link name when starting nagios. echo 'set from='$POSTFIX_ENV_MAIL >> /etc/nail.rc cp /etc/mailrc $NAGIOS_HOME/.mailrc chown nagios:nagios $NAGIOS_HOME/.mailrc chown nagios:nagios /etc/nail.rc fi # remove localhost configuration (by default is enabled) rm -f $NAGIOS_HOME/etc/objects/localhost.cfg sed -i "s|cfg_file=/opt/nagios/etc/objects/localhost.cfg|#cfg_file=/opt/nagios/etc/objects/localhost.cfg|g" $NAGIOS_HOME/etc/nagios.cfg # add timezone check sed -i 's|use_timezone=|#use_timezone=|g' $NAGIOS_HOME/etc/nagios.cfg # start nagios /usr/local/bin/start_nagios
Our Nagios image is ready! Now let’s create our configuration image with this Dockerfile:
# Docker Nagios Conf # # VERSION 1.0 #INSTRUCTION # scratch is a minimal docker image, ideal to hold configuration files. FROM scratch MAINTAINER Tiago Pires, tandrepires@gmail.com ADD configuration-file.cfg /conf/ VOLUME [ "/conf" ]
This image holds our configuration file(s) and now we can start it and import its volume!
Let’s first create our images.
$ cd nagios $ docker build -t myrepo/nagios . $ cd conf $ docker build -t myrepo/nagios-conf .
Now let’s put it to work, by first running our configuration image and then import its volume:
$ docker run -d --name nagios-conf myrepo/nagios-conf /dev $ docker run -d --name nagios -e CONF_PATH=/conf -e NAGIOSADMIN_PASS=myownpassword -e HOME=/root --volumes-from nagios-conf -v /etc/localtime:/etc/localtime -p 8080:80 myrepo/nagios # if you've an external postfix image add: --link postfix:postfix
We’re starting our Nagios container setting its configuration path (CONF_PATH), modifying the default password (NAGIOSADMIN_PASS), setting HOME directory, importing configuration files, synchronizing with system localtime and setting 8080 as our external port.
Let’s browse to http://localhost:8080 and Nagios should be up and running!
Filed under Tech
XBMC has released today the long waited XBMC 12 “Frodo”. It has support for Linux, Windows, Mac OS X, Android, Raspberry Pi, Apple TV and Apple iOS.I’ve already compiled it from Raspberry Pi (NOT OFFICIAL links below).
Filed under Tech
I’m proud to say that i’ve been selected to another awesome edition of SAPO Codebits! I’ve participated on Codebits before and let me tell you it’s awesome! Three days that look like one. Forget sleeping, just enjoy! I’m also excited for the fact that Raspberry Pi guys will be there and i’ll have a great opportunity to “feel” the project even closer 😉
Let the *fun* begin! 😀
OpenELEC build r12431 has already a nice media_build support, so you don’t need to add media_build support anymore. I’ve already updated my guide, so you won’t get all confused.
Download here the latest OpenELEC build to the moment (r13118).
Filed under Tech
Geek for a day 