====== Command cheatsheet ======

===== su to user with no login shell =====

To become a user that has /bin/false as shell:

  # su - user -s /bin/<some shell>

===== find duplicate lines in a file =====

  $ sort FILE | uniq -D

(Must sort since ''uniq'' will only look at consecutive lines)

Can also limit the number of characters to compare, e.g. 20 characters:

  $ sort FILE | uniq -D -w 20

source: http://www.linuxquestions.org/questions/linux-software-2/finding-duplicate-lines-in-a-file-617441/

==== find duplicate files ====

The method above can be used with a list of hashes to locate identical files:

  $ md5sum * > MD5SUMS
  $ sort MD5SUMS | uniq -D -w 32

===== CD/DVD imaging =====

==== ISO extraction ====

Source: [[http://www.noah.org/wiki/Dd_-_Destroyer_of_Disks#Image_a_CD_or_DVD|Dd - Destroyer of disks]]

(A simple ''dd'' will work but might carry some extra garbage)

Discover sector size (2048 for standard ISOs) and ISO size:
  $ isoinfo -d -i /dev/cdrom
  ... # e.g.:
  Logical Block Size: 2048    # <- sector size
  ...
  Volume Space Size: 123456    # ISO size
  $ dd if=/dev/cdrom bs=2048 count=123456 conv=noerror of=image.iso

''conv=notrunc'' Appends to output 
''conv=noerror'' Continues after read errors
\\
(can be combined with ''conv=notrunc,noerror'')

==== Dump VideoCD ====

  $ vcdxrip -C     # Part of vcdimager