Simple, easily extensible, /var/log backup script

varlogbackup.sh

#!/bin/bash

# Variables (aka config)
# Script executed after making backup of /var/log (none for no script to execute)
passScript=""
# Remove syslog, auth.log, kern.log, after backup? ("true"/"false")
removeAfterVarlog="true"
# Remove backup tar from /tmp. Good when uploading with passScript ("true"/"false")
removeAfterTar="false"

err_exit () {
	echo "Exiting..."
	exit
}

# Check if we can read /var/log files
if [ -d "/var/log" ]; then
	echo "/var/log Exists"
else
	echo "[ERR] /var/log Does not exist!"
	err_exit
fi

for i in "auth.log" "kern.log" "syslog"
do
	if [ -r "/var/log/$i" ]; then
		echo "/var/log/$i Is readable"
	else
		echo "[ERR] /var/log/$i Does not exist, or is not readable!"
		err_exit
	fi
done

# Check if we have every command we need
for i in "du" "md5sum" "tail" "tar" "xz"
do
	if [ -x "$(command -v $i)" ]; then
		echo "Found $i"
	else
		echo "[ERR] $i Not found, or not executable!"
		err_exit
	fi
done

# Check how much space will tar take
tarSpace=$(du -hc /var/log | tail -1)
echo "Backup will take around $tarSpace"

# Check if /tmp exists, check if theres no another file with same name, and write a tar archive
if [ ! -d "/tmp" ]; then
	echo "[ERR] /tmp Does not exist! What the hell?!"
	err_exit
fi

echo "Making tar archive of /var/log..."
tarFileName="$(date "+%d.%m.%y_%R")_varlog.tar"
echo "Name: /tmp/$tarFileName"
if [ -f /tmp/$tarFileName ]; then
	echo "[ERR] /tmp/$tarFileName exists!"
	err_exit
fi
tar cvf /tmp/$tarFileName /var/log/*
xz /tmp/$tarFileName
tarFileName="$tarFileName.xz"

# Check if /tmp/tar is made properly
if [ ! -f /tmp/$tarFileName ]; then
	echo "[ERR] /tmp/$tarFileName does not exist! Something went wrong!"
	err_exit
fi

# Make md5sum of backup tar
printf "md5: "
md5sum /tmp/$tarFileName

# Execute another script with tar filename passed
## This is used for remote backup, or whatever you want to do with backup file
if [ ! $passScript = "" ]; then
	echo "Running $passScript"
	$passScript "/tar/$tarFileName"
else
	echo "No passScript specified"
fi

# Remove things from /var/log		**CRITICAL**
if [ $removeAfterVarlog = "true" ]; then
	echo "Removing old logs..."
	rm /var/log/kern.log* /var/log/auth.log* /var/log/syslog*
fi

# Remove backup file
if [ $removeAfterTar = "true" ]; then
	echo "Removing backup tar..."
	rm /tmp/$tarFileName
fi

# Done
echo "Done, have a nice day"