Linux

Merge Two or More PDFs into a New Document

pdftk 1.pdf 2.pdf 3.pdf cat output 123.pdf

CHROOT from Live CD

mount /dev/ /mnt
mount -t proc none /mnt/proc
mount -o bind /dev /mnt/dev
chroot /mnt /bin/bash
mount -a

Share an X11 Session via VNC

x11vnc -display :0

Show Firewire Devices

plugreport

Sort groups by GID

cat /etc/group | sort -t : -k 3 -n

Get next local UID

cat /etc/passwd | grep -v nobody | awk -F : '{print $3}' | sort -n | tail -n 1 | awk '{print $1+1}'

Get next local GID

cat /etc/group | grep -v nogroup | awk -F : '{print $3}' | sort -n | tail -n 1 | awk '{print $1+1}'

Send Gratuitous ARP Packet

arping -c 1 ip-address

Time Lapse Picures

motion.config:

snapshot_interval 60
output_normal discrete off
height 1024
width 1280

motion -c motion.config

Entropy

If entropy_avail is consistently low, install rng-tools. This is designed to use a hardware random number generator, but in the absence of that, it can "fake" it by using /dev/urandom to generate entropy with the following command.

/usr/sbin/rngd -s 64 -t 60 -b -r /dev/urandom

Escape spaces in a variable

"$(echo "$VAR" | sed 's/[ ]/\\\ /g')"

Convert lower case to upper case

echo $1 | tr "[:lower:]" "[:upper:]"

Convert upper case to lower case

echo $1 | tr "[:upper:]" "[:lower:]"

Recursively rename all files in a directory to all lowercase

IFS="
"; for x in `find /path/to/directory`; do mv "$x" "`echo $x | tr \"[:upper:]\" \"[:lower:]\"`"; done

Force script to run as root

if [ `whoami` != "root" ]; then
    sudo $0 $*
    exit
fi

Convert hex to decimal

echo $((0x15a))

SELinux

Disable SELinux in grub by appending the following to the kernel line

selinux=0

Create pcap file

tcpdump -nn -w tcpdump.pcap -s0 *rules*

Create AVI from JPG files

mencoder "mf://*.jpg" -mf fps=4 -ovc lavc -o movie.avi

mencoder "mf://*.jpg" -mf fps=30 -ovc lavc -lavcopts vcodec=msmpeg4v2:vbitrate=4900 -o movie.avi