Create user and password on Linux non interactive and add it to sudo a tiny Dev Ops script

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A common task for SysAdmins who managed a multitude of servers remotely via Secure Shell was to add a user and assign password by using a script, this was sometimes necessery to set-up some system users and create access for university users on 10 / 20 testing Linux servers.

Nowadays this task of adding user to a list of remote servers and granting the new user superuser permissions through /etc/sudoers is practiced heavily by the so called Dev Ops (Just another Buziness Word for Senior System Admiistrators with good scripting skills and a little bit of development experience – same game different name.

The Dev Ops System Integration Engineers use this useful add non-interactive user via SSH in Cloud environments in order to prepare superuser (root permissioned through /etc/sudoers) user, that is later be used for lets say deployment on a few hundred of servers of lets say LAMP (Linux + Apache + MySQL + PHP) or LEMP (Linux NGINX MySQL PHP) or Software Load Balancer HAProxy  balacing for MySQL clusters / Nginx Application servers / JIRAs etc, through a Playbook script with some deployment automation tool such as Ansible.

Well enough talk here is the few lines of code which does create a user locally:
 

linux:~# apt-get install –yes sudo
linux:~# useradd devops –home /home/devops -s /bin/bash
linux:~# mkdir /home/devops
linux:~# chown -R devops:devops /home/devops
linux:~# echo 'username:testpass' | chpasswd


Though this lines could be invoked easily by passing it as arguments via ssh it is often unhandy to run them on remote host, because some of the remote hosts against executed, might have already the user existent with granted permissions for sudo

Thus a much better way to do things is use below script and first upload it to remote servers by running the scp command in a loop:

while read line; do
scp  root@$i:/root/
ssh "
create_user_noninteractive_and_add_to_sudoers.sh"
done < servers_list.txt


Where servers_list.txt contains a list of remote IPs:

#!/bin/bash
# Create new user/group and add nopasswd login to sudoers
# Author: Georgi Georgiev
# has to be run sa root – sudo devops
# hipo@pc-freak.net

 

u_id='devops';
g_id='devops';
pass='testpass';
sudoers_f='/etc/sudoers';

check_install_sudo ()  {
if [ $(dpkg –get-selections | cut -f1|grep -E ‘^sudo’) ]; then
apt-get install –yes sudo
else
        printf "Nothing to do sudo installed";
fi
}

check_install_user () {

if [ “$(sed -n “/$u_id/p” /etc/passwd|wc -l)” -eq 0 ]; then
apt-get install –yes sudo
apt-get install –yes sudo
useradd $u_id –home /home/$u_id
mkdir /home/$u_id
chown -R $u_id:$g_id /home/$u_id
echo "$u_id:$pass" | chpasswd
cp -rpf /etc/bash.bashrc /home/$u_id
if [ “$(sed -n “/$u_id/p” $sudoers_f|wc -l)” -eq “0” ]; then
echo "$u_id ALL=(ALL) NOPASSWD: ALL" >> $sudoers_f
else
        echo "$u_id existing. Exiting ..";
        exit 1;
fi

else
        echo "Will do nothing because $u_id exists";
fi

}

check_install_sudo;
check_install_user;


By the way this task was the simplest task given by a Company where I applied for a Dev Ops System Engineer, so I hope this will help someone else too.

P.S. If you prefer Shell scripts (even though much harder, time consuming etc.) as a mean of automation as an alternative to Ansible / Chef I suggest you check out and perhaps try to do the task with http://fuckingshellscripts.org 🙂

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