5 Important scripts useful for a Linux system administrator

While all the scripts provided below may be accurate, there may be much more advanced features available. However, these scripts are just to give an overview of how things are meant to be done for a systems administrator. I did not make any of the below scripts and all scripts’ references are given inline along with their description.

Disk usage

This script will be useful to analyze the disk usage and if the reported disk space is more than 90 % an email will be sent to the administrator. The script is taken from here.

# set -x
# Shell script to monitor or watch the disk space
# It will send an email to $ADMIN, if the (free available) percentage of space is >= 90%.
# -------------------------------------------------------------------------
# Set admin email so that you can get email.
# set alert level 90% is default
# Exclude list of unwanted monitoring, if several partions then use "|" to separate the partitions.
# An example: EXCLUDE_LIST="/dev/hdd1|/dev/hdc5"
function main_prog() {
while read output;
#echo $output
  usep=$(echo $output | awk '{ print $1}' | cut -d'%' -f1)
  partition=$(echo $output | awk '{print $2}')
  if [ $usep -ge $ALERT ] ; then
     echo "Running out of space \"$partition ($usep%)\" on server $(hostname), $(date)" | \
     mail -s "Alert: Almost out of disk space $usep%" $ADMIN
if [ "$EXCLUDE_LIST" != "" ] ; then
  df -H | grep -vE "^Filesystem|tmpfs|cdrom|${EXCLUDE_LIST}" | awk '{print $5 " " $6}' | main_prog
  df -H | grep -vE "^Filesystem|tmpfs|cdrom" | awk '{print $5 " " $6}' | main_prog

Incremental Backup Scripts

This script will do the incremental backup into an external mounted hard-drive. It is to take a backup of the /home directory. However, it can be modified to suit the requirements. The script is taken from here.

# ----------------------------------------------------------------------
# mikes handy rotating-filesystem-snapshot utility
# ----------------------------------------------------------------------
# this needs to be a lot more general, but the basic idea is it makes
# rotating backup-snapshots of /home whenever called
# ----------------------------------------------------------------------

unset PATH  # suggestion from H. Milz: avoid accidental use of $PATH

# ------------- system commands used by this script --------------------



# ------------- file locations -----------------------------------------


# ------------- the script itself --------------------------------------

# make sure we're running as root
if (( `$ID -u` != 0 )); then { $ECHO "Sorry, must be root.  Exiting..."; exit; } fi

# attempt to remount the RW mount point as RW; else abort
if (( $? )); then
    $ECHO "snapshot: could not remount $SNAPSHOT_RW readwrite";

# rotating snapshots of /home (fixme: this should be more general)

# step 1: delete the oldest snapshot, if it exists:
if [ -d $SNAPSHOT_RW/home/hourly.3 ] ; then         \
$RM -rf $SNAPSHOT_RW/home/hourly.3 ;                \
fi ;

# step 2: shift the middle snapshots(s) back by one, if they exist
if [ -d $SNAPSHOT_RW/home/hourly.2 ] ; then         \
$MV $SNAPSHOT_RW/home/hourly.2 $SNAPSHOT_RW/home/hourly.3 ; \
if [ -d $SNAPSHOT_RW/home/hourly.1 ] ; then         \
$MV $SNAPSHOT_RW/home/hourly.1 $SNAPSHOT_RW/home/hourly.2 ; \

# step 3: make a hard-link-only (except for dirs) copy of the latest snapshot,
# if that exists
if [ -d $SNAPSHOT_RW/home/hourly.0 ] ; then         \
$CP -al $SNAPSHOT_RW/home/hourly.0 $SNAPSHOT_RW/home/hourly.1 ; \

# step 4: rsync from the system into the latest snapshot (notice that
# rsync behaves like cp --remove-destination by default, so the destination
# is unlinked first.  If it were not so, this would copy over the other
# snapshot(s) too!
$RSYNC                              \
    -va --delete --delete-excluded              \
    --exclude-from="$EXCLUDES"              \
    /home/ $SNAPSHOT_RW/home/hourly.0 ;

# step 5: update the mtime of hourly.0 to reflect the snapshot time
$TOUCH $SNAPSHOT_RW/home/hourly.0 ;

# and thats it for home.

# now remount the RW snapshot mountpoint as readonly

if (( $? )); then
    $ECHO "snapshot: could not remount $SNAPSHOT_RW readonly";
} fi;

High CPU Usage Script

At times, we need to monitor the high CPU usage in the system. We can use the below script to monitor the high CPU usage. The script is taken from here.

while [ true ] ;do
used=`free -m |awk 'NR==3 {print $4}'`

if [ $used -lt 1000 ] && [ $used -gt 800 ]; then
echo "Free memory is below 1000MB. Possible memory leak!!!" | /bin/mail -s "HIGH MEMORY ALERT!!!" user@mydomain.com

sleep 5

Adding new users to a Linux system

This script allows the root user or admin to add new users to the system in an easier way by just typing the user name and password (The password is entered in an encrypted manner). The below script is taken from here.

# Script to add a user to Linux system
if [ $(id -u) -eq 0 ]; then
    read -p "Enter username : " username
    read -s -p "Enter password : " password
    egrep "^$username" /etc/passwd >/dev/null
    if [ $? -eq 0 ]; then
        echo "$username exists!"
        exit 1
        pass=$(perl -e 'print crypt($ARGV[0], "password")' $password)
        useradd -m -p $pass $username
        [ $? -eq 0 ] && echo "User has been added to system!" || echo "Failed to add a user!"
    echo "Only root may add a user to the system"
    exit 2

Database Backup

This script is a pretty basic script useful in backing up the database. The script is taken from here.

now="$(date +'%d_%m_%Y_%H_%M_%S')"
logfile="$backupfolder/"backup_log_"$(date +'%Y_%m')".txt
echo "mysqldump started at $(date +'%d-%m-%Y %H:%M:%S')" >> "$logfile"
mysqldump --user=mydbuser--password=mypass --default-character-set=utf8 mydatabase | gzip > "$fullpathbackupfile"
echo "mysqldump finished at $(date +'%d-%m-%Y %H:%M:%S')" >> "$logfile"
chown myuser "$fullpathbackupfile"
chown myuser "$logfile"
echo "file permission changed" >> "$logfile"
find "$backupfolder" -name db_backup_* -mtime +8 -exec rm {} \;
echo "old files deleted" >> "$logfile"
echo "operation finished at $(date +'%d-%m-%Y %H:%M:%S')" >> "$logfile"
echo "*****************" >> "$logfile"
exit 0

Source : http://unix.stackexchange.com/questions/125726/important-scripts-useful-for-a-linux-system-administrator

Script : Color_bash.sh

Travaillant actuellement sur une fonction d’affichage pour les scripts bash, je vous partage un petit qui vous affichera dans le terminal les couleurs et leur code associé en bash.

#   This file echoes a bunch of color codes to the
#   terminal to demonstrate what's available.  Each
#   line is the color code of one forground color,
#   out of 17 (default + 16 escapes), followed by a
#   test use of that color on all nine background
#   colors (default + 8 escapes).
#   Author: Giles Orr
#   URL: http://gilesorr.com/bashprompt/howto/c350.html
#   License: GNU Free Documentation License, Version 1.1 or any later version published by the Free Software Foundation;
#            http://gilesorr.com/bashprompt/howto/a1004.html

T='gYw'   # The test text

echo -e "\n                 40m     41m     42m     43m\
     44m     45m     46m     47m";

for FGs in '    m' '   1m' '  30m' '1;30m' '  31m' '1;31m' '  32m' \
           '1;32m' '  33m' '1;33m' '  34m' '1;34m' '  35m' '1;35m' \
           '  36m' '1;36m' '  37m' '1;37m';
  do FG=${FGs// /}
  echo -en " $FGs \033[$FG  $T  "
  for BG in 40m 41m 42m 43m 44m 45m 46m 47m;
    do echo -en "$EINS \033[$FG\033[$BG  $T  \033[0m";

echo -e "\e[0mNO_COLOR"
echo -e "\e[1;37mCOLOR_WHITE\t\e[0;30mCOLOR_BLACK"
echo -e "\e[0;34mCOLOR_BLUE\t\e[1;34mCOLOR_LIGHT_BLUE"
echo -e "\e[0;32mCOLOR_GREEN\t\e[1;32mCOLOR_LIGHT_GREEN"
echo -e "\e[0;36mCOLOR_CYAN\t\e[1;36mCOLOR_LIGHT_CYAN"
echo -e "\e[0;31mCOLOR_RED\t\e[1;31mCOLOR_LIGHT_RED"
echo -e "\e[0;35mCOLOR_PURPLE\t\e[1;35mCOLOR_LIGHT_PURPLE"
echo -e "\e[0;33mCOLOR_YELLOW\t\e[1;33mCOLOR_LIGHT_YELLOW"
echo -e "\e[1;30mCOLOR_GRAY\t\e[0;37mCOLOR_LIGHT_GRAY"

skynet.tomzone.fr - PuTTY_2

Source : https://github.com/fikovnik/bin-scripts

Bash – Utiliser une regex pour vérifier une date

Dernièrement, pour le besoin d’un script, il me fallait créer une regex pour check que les dates étaient valide.

Voici la regex que j’ai utilisé


Il suffit ensuite de le mettre dans un while et d’ajouter un read pour avoir une boucle qui pose et repose la question tant que la date entrée dans le terminal n’est pas valide.

J’utilise dans ce cas la le format de date anglais YYYY-MM-DD

Continuer la lecture de Bash – Utiliser une regex pour vérifier une date