ls -R

Unusual Tasks With File Listings

When you create a new GPG key it wants you to wiggle the mouse or pound the keyboard or do something to create enough entropy to create a well-randomized key. There is an easy way, and that is to use the ls command to recursively list every file on your system:

$ ls -R /

Do this in a separate terminal, and then you don't have to do silly tiring things like wiggling mice. While we're on the subject of the ls command, you can list multiple directories in a single command by using simple wildcards:

$ sudo ls -l /var/*/*/

You can skip over subdirectories, as this example shows:

$ sudo ls -l /var/.../*/

I'm sure I copied this one from somewhere-- It draws a nice ASCII file tree of all subdirectories of the current directory:

$ find . -type d |sed 's:[^-][^/]*/:--:g; s:^-: |:'

Find Duplicate Files

The sure-fire way to find duplicate files is by comparing MD5 hashes. This compares only the first 20 characters of the md5sum, but it still takes a long time. It's the most accurate method, so I don't mind the wait:

$ find . -type f -exec md5sum '{}' ';' | sort | uniq --all-repeated=separate -w 20

You can also compare file sizes, which is a little less accurate but a lot faster:

$ find . -type f -printf "%p - %s" | sort -nr -k3 | uniq -D -f1

I use the first method when I start accumulating a lot of sloppy backups, and have too many copies of the same files littering my backup servers.
Find more here
https://www.linux.com/learn/docs/660651-bag-of-fun-and-useful-random-linux-comman
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Thanks and Regards
Bhaskar Ramaraju
http://www.linkedin.com/in/ramarajubhaskar