systemctl enable and start service

Most of the times when I want to enable the service, I find myself enabling it immediately or it is vice versa. So, the commands I used to use were:

systemctl enable sshd.service
systemctl start sshd.service

But recently I learned that I do not need the 2 commands and this can be done in single command like below

1
 

systemctl enable --now sshd.service

Display IP address in console login screen

Here is one liner that will add the current IP address in the console login screen (if you are not running X as is case for servers):

 (ip -o -4 a| awk '$2 !="lo" {print "\nIP Address ::"$4}' |tr '\n' ',';echo)>>/etc/issue

Just execute the above command as root. It will add the required code in “/etc/issue” to display the IP address. BTW, you can also use “\4” or “\6” instead of that command to get the IP but that will not work with some old versions of Linux.

Linked clone with qemu-img

As you would have seen in Virtualbox or vmware, there is option to create a linked clone. I wanted to use the same feature as “Snapshot” feature anyway does not look/work so great with virt-manager. So, I created a script to create a linked clone VM and here it is :

 

#!/bin/bash - 
#===============================================================================
#
#          FILE: qcow2-linked-clone.sh
# 
#         USAGE: ./qcow2-linked-clone.sh 
# 
#   DESCRIPTION: 
# 
#       OPTIONS: ---
#  REQUIREMENTS: ---
#          BUGS: ---
#         NOTES: ---
#        AUTHOR: Amit Agarwal (aka)
#  ORGANIZATION: Mobileum
#       CREATED: 01/05/2018 09:54
# Last modified: Wed Feb 28, 2018  04:39PM
#      REVISION:  ---
#===============================================================================

set -o nounset                              # Treat unset variables as an error
UP="amitag:amitag" #Here you need to put your username and group.

if [[ $# == 0 ]]
then
    read -p "Enter the source path :: " spath
    read -p "Enter the source disk :: " sdisk
    read -p "Enter the destin path :: " dpath
    read -p "Enter the destin disk :: " ddisk
    read -p "Enter new VMName :: " vmname
else
    spath=$(dirname $1)
    dpath=$spath
    sdisk=$(basename $1)
    ddisk=$2.qcow2
    vmname=$2
fi


sudo chown $UP "$spath/$sdisk"
qemu-img create -f qcow2 -b "$spath/$sdisk" "$dpath/$ddisk"

virt-install --disk $dpath/$ddisk --ram 512 \
    --virt-type kvm --vcpus 1 --name "$vmname" --import

The script will create a linked qcow2 and then create a VM with that image. Running it is simple, either provide command line options or just run and it will ask you for details.

 

Hope it is useful.