script for backing up a system, I personally ignore home because I don't keep anything important in there - I just clean install when needed. To extract the file, replace `-c` with `-x` and specify the destination (note: this will overwrite existing files)

backup.sh

: ${DESTINATION_DIRECTORY:=}                                                                                                             [0/0]
: ${BACKUP_FILENAME:=$(date +%Y%m%d%H%M%S)-backup.tar.gz}    

tar -czpvf $DESTINATION_DIRECTORY/$BACKUP_FILENAME \
    --exclude=/proc \
    --exclude=/tmp \
    --exclude=/mnt \
    --exclude=/dev \
    --exclude=/sys \
    --exclude=/run \
    --exclude=/var \
    --exclude=/usr \
    --exclude=/home /

https://help.ubuntu.com/community/BackupYourSystem/TAR

tar - is the command that creates the archive. It is modified by each letter immediately following, each is explained below.

c - create a new backup archive.
v - verbose mode, tar will print what it's doing to the screen.
p - preserves the permissions of the files put in the archive for restoration later.
z - compress the backup file with 'gzip' to make it smaller.
f - specifies where to store the backup, backup.tar.gz is the filename used in this example. It will be stored in the current working directory, the one you set when you used the cd command.