30+ useful Linux commands list

This collection of commands are some of the commands I have learned in these years. Of course I am not the author of them, as no one is the author of any command in Linux. I have found some of them in differente pages, and modify some of them, others I have "created" by myself. Reading books, or man pages. Disclaimer: Try any of these commands, in non-production servers, some of them may break something Add yours in the comments.

1. Purge configuration files of Debian's removed packages

There are different ways to do this, these are some options.sudo aptitude purge '~c' sudo dpkg -l | awk '/^rc/ {print $2}' | xargs dpkg -P

2. Create movies from jpg files

mencoder "mf://*.jpg" -mf fps=10 -o test.avi -ovc lavc -lavcopts vcodec=msmpeg4v2:vbitrate=800

3. Empty (erase contents) of a file

Once again there are different ways to do this::> file truncate -s0 file

4. Find duplicate files, based on size and MD5

find -not -empty -type f -printf "%s\n" | sort -rn | uniq -d | xargs -I{} -n1 find -type f -size {}c -print0 | xargs -0 md5sum | sort | uniq -w32 --all-repeated=separate

5. Replace space on file names with underscores

#!/bin/bash

ls | while read -r FILE
do
    mv -v "$FILE" `echo $FILE | tr ' ' '_' `
done

6. Convert a man page to txt file

man cp | col -b > /tmp/man-cp.txt change cp for any command you want to have its man page in text format.

7. List the most used commands in your history

history | awk '{print $2}' | sort | uniq -c | sort -rn | head

8. Execute a command, and do not save it in history

command

9. Attach a clock to the command line prompt

export PS1="${PS1%\\\$*}"' \t \$ ' The output will look like this:

[ggarron@arch ~] 16:13:14 $

10. Force file system check

sudo touch /forcefsck orsudo shutdown -rF now

11. Create and mount a RAM disk

mount -t tmpfs tmpfs /mnt -o size=1024m That will create a 1 Gig RAM disk, that you can use to have fast access to files there, just remember is a RAM disk, and all its contents will be deleted when the system is rebooted.

12. Call commands from History

You may call command from history by numbers:class="codigo">history

963  du -h
  964  ls
  965  df
  966  htop
  967  df -h
  968  df -h 
  969  history

Then using the number call a command:!963 Or call it by using the first letters:!df This last method, is somehow dangerous, as you do not know what arguments and options the command is going to use, so, you can pause it. Using this way is safer:!df:p It shows you the command but do not run, it, then, you can run it without the :p and it will run, but this time you know the options.

13. Count lines and words in a text document

wc -l -w mytextfile.txt

14. Mount a remote file system via ssh

sshfs remote-user@remote.server:/remote/directory /mnt/remote-fs/ More info: here

15. Copy ssh public key to a server to access it with no ssh password

cat ~/.ssh/id_rsa.pub | ssh user@remote.machine "mkdir ~/.ssh; cat >> ~/.ssh/authorized_keys" More info: here

16. Generate random passwords

dd if=/dev/urandom bs=16 count=1 2>/dev/null | base64 With 16 characters, if you want only 8.dd if=/dev/urandom bs=8 count=1 2>/dev/null | base64

17. Update Twitter from the command line

curl --basic --user "user:pass" --data-ascii "status=Arriving the office" "http://twitter.com/statuses/update.json"

18. Replace words in a document using sed

sed -i 's/OLD/NEW/g' FILE More info here

19. List type of network connections active and the number of them

netstat -ant | awk '{print $NF}' | grep -vE '[:upper:]'| sort | uniq -c | sort -rn Output:

35 TIME_WAIT
     27 ESTABLISHED
      2 LISTEN
      2 CLOSE_WAIT

20. Mount an iso image as disk

mount -t iso9660 -o loop file.iso /media/disk

21. Reset the terminal, when it get screwed, and you can only see garbage on it

reset

22. List all processes with stablished connections

lsof -i -n | grep ESTABLISHED More info here

23. Backup a disk or partition to an image

dd if=/dev/sda of=~/backup-disk-YY-MM-DD.img More info here

24. Simple HTTP server to share files

python -m SimpleHTTPServer

25. Change the layout of you keyboard on the fly

setxkbmap -layout us

26. Read a compressed file on the fly, without uncompressing it

zcat file.gz

27. Use lynx to store web pages as text

lynx -dump http://www.go2linux.org > $HOME/go2linux.txt

28. Determining the type of file

file *

29. make commands keep running after leaving a terminal session or ssh session

nohup nice -n 4 [command] > output.txt & More info here

30. Recreate fluxbox menu

fluxbox-generate_menu