Some useful tips

Tip1. Single command to set user password:-

# usermod -p $(echo newpass | openssl passwd -1 -stdin) u1

Tip2. Recovering deleted images from flash cards:-

# aptitude update

# aptitude install testdisk

The tool which we are using is "photorec". Now we are going to remount the flash disk.

# dd if=/dev/sdd1 of=disk.img bs=1024M

# mkdir ./recovered

# photorec /d ./recovered disk.img

The recovered file will be in the directory ./recovered. 

Tips. Securely erasing files, by filling your disk:-

# aptitude update

# aptitude install secure-delete

Once installed you can overwrite the unused content of any mounted partition like so:

# sfill /home

# mount | grep /dev

Once completed, the huge file is removed, meaning you have free disk space again.