Cloud DevOps Admin Guide

Modern way of /etc/motd - FireMotd for linux

While developing, playing or working on Linux systems, a dynamic MotD generator script can quickly give you an overview of all used components of your Linux systems.

FireMotD can show you this information in a sanitized and colorful way while you log in with SSH or console.
Depending of the chosen theme FireMotD will output all information defined in the theme on your server.
We need EPEL repository to be installed and enabled in the server to install the dependency packages.

Install Dependencies

You need to install the required dependencies as shown below.

yum install bc sysstat jq moreutils

After installing the dependencies, clone/download or copy the FireMotd to the root directory as shown.

git clone https://github.com/OutsideIT/FireMotD.git

Change to the FireMotd directory and run the below commands

You need to have make installed on the system, if you want to use the Makefile.

To install to /usr/local/bin/FireMotD

sudo make install

With this you can probably run FireMotD from anywhere in your system. If not, you need to add /usr/local/bin to your $PATH variable. To adjust the installation path, change the var IDIR=/usr/local/bin in the Makefile to the path you want.

To install bash autocompletion support

sudo make bash_completion

With this you can use TAB to autocomplete parameters and options with FireMotD. Does not require the sudo make install above (system install), but requires the bash-completion package to be installed and working. Then you should logout-login or source the bash completion file, eg. $ . /etc/bash_completion.d/FireMotD

If you don't have root access, just install everything on your user's folder and source the file from your user's .profile file

Crontab to get system information

Root privilege is required for this operation. Only /etc/crontab and the files in /etc/cron.d/ have a username field.

The recommended way to generate /var/tmp/FireMotD.json is by creating a separate cron file for firemotd like this:

sudo vim /etc/cron.d/firemotd

# FireMotD system updates check (randomly execute between 0:00:00 and 5:59:59) 0 0

* * * root perl -e 'sleep int(rand(21600))' && /usr/local/bin/FireMotD -S &>/dev/null

But you can also put it in root's crontab (without the user field):

sudo crontab -e

# FireMotD system updates check (randomly execute between 0:00:00 and 5:59:59) 0 0

* * * perl -e 'sleep int(rand(21600))' && /usr/local/bin/FireMotD -S &>/dev/null

Adding FireMotD to run on login

Choosing where to run your script is kind of situational. Some files will only run on remote logins, other local logins, or even both. You should find out what suits best your needs on each case.

To add FireMotD to a single user

Edit the user's ~/.profile file, ~/.bash_profile file, or the ~/.bashrc file
nano ~/.profile

Add the FireMotD call at the end of the file (choose your theme)

/usr/local/bin/FireMotD -t blue

To add FireMotD to all users

You may call FireMotD from a few different locations for running globally.
Eg./etc/bash.bashrc, /etc/profile.

we use /etc/profile, so add the line to this file.

Color outputs :

Blue

Red

Gray

Enable EPEL Repository for RHEL/CentOS 7.x

What is EPEL

EPEL (Extra Packages for Enterprise Linux) is open source and free community based repository project from Fedora team which provides 100% high quality add-on software packages for Linux distribution including RHEL (Red Hat Enterprise Linux) and CentOS.

Epel project is not a part of RHEL/CentOS but it is designed for major Linux distributions by providing lots of open source packages like networking, sys admin, programming, monitoring and so on. Most of the epel packages are maintained by Fedora repo.

Why we use EPEL repository?

Provides lots of open source packages to install via Yum.
Epel repo is 100% open source and free to use.
It does not provide any core duplicate packages and no compatibility issues.
All epel packages are maintained by Fedora repo.

How To Enable EPEL Repository in RHEL/CentOS 7?

First, you need to download the file using Wget and then install it using RPM on your system to enable the EPEL repository. Use below links based on your Linux OS versions. (Make sure you must be root user).

# wget http://dl.fedoraproject.org/pub/epel/epel-release-latest-7.noarch.rpm # rpm -ivh epel-release-latest-7.noarch.rpm

You need to run the following command to verify that the EPEL repository is enabled. Once you ran the command you will see epel repository.

# yum repolist

Add SWAP to Linux VM’s on Azure

Every virtual machine (VM) on Azure has what we call a temporary (ephemeral) disk which is recommended to be used ONLY as temporary storage and that includes SWAP files or data that does not need to be available upon a reboot or saved , the data stored in this drive will be lost.
To create a swap file in the directory that's defined by the ResourceDisk.MountPoint parameter, you can update the /etc/waagent.conf file by setting the following three parameters:

ResourceDisk.Format=y
ResourceDisk.EnableSwap=y
ResourceDisk.SwapSizeMB=xx

Note The xx placeholder represents the desired number of megabytes (MB) for the swap file.
Where the size is in MB, so for instance, to create a SWAP file of 4GB you could use these lines:

ResourceDisk.Format=y
ResourceDisk.EnableSwap=y
ResourceDisk.SwapSizeMB=4096

Restart the WALinuxAgent service by running one of the following commands, depending on the system in question:

Ubuntu: service walinuxagent restart

Red Hat/Centos: service waagent restart

Run one of the following commands to show the new swap apace that's being used after the restart:

dmesg | grep swap
swapon -s
cat /proc/swaps
file /mnt/resource/swapfile
free| grep -i swap