My first experience with Linux started when i setuped a server for one my client. It was monumental task for me at that time. I was very happy mouse driven windows user. When I came to the world of putty I was lost. So I had to search for certain commands. I recently written the Setup LAMP With Ubuntu In 10 Minutes. One of my colleague trie to setup LAMP following that post. He was also happy mouse driven windows user So he was having problem with commands. So in this post I am showing all the commands I need and used to use Linux server. I will post all the problems i faced using LAMP in next post. Be sure to subscribe my blog.

To create new directory

mkdir target_director

To copy an entire folder (directory tree) in Linux

cp -ap /var/lib/mysql /mnt/mysql -ap for same permission as source

For checking the size of current folder

du -ch | grep total

To find the size of the hdd

 just enter df

To find out the size of the folder in the folder

du
du -a to show all the file's size

See all files and their size

du -s * -h

To output the number of files in the current directory 

ls | wc -l

See all the jobs

ps -aux

To find out RAM size on Linux machine

free

Rename folder/filename

mv test hope
mv *.rtf *.txt

To find which process is consuming how much RAM?

top

To see the free ram memory

free -m

To update yum using corn 

0 21 *** usr/bin/yum -y update

Create tar.gz file

tar czvf myfolder.tar.gz abcfolder/

Untar a tar file
tar czvf myfolder.tar.gz abcfolder/
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Delete bash History
Try to delete the content of ~/.bash_history

To add new user
* Adding a new user (useradd)
* Modifying an existing user (usermod)

Options:
* -d home directory
* -s starting program (shell)
* -p password
* -g (primary group assigned to the users)
* -G (Other groups the user belongs to)
* -m (Create the user’s home directory

useradd -gusers -Gmgmt -s/bin/shell -pass -d/home/jambura -m jambura

User’s home directory should be 700. If you are operating a ~username type server, the public_html directory should be 777. You may also need to open up the home directory to 755.

 useradd -s/bin/bash -pass -d/imp/sysbsd -m sysbsd

For allowing sudo

 sudo adduser jambura admin

To delete user

userdel user

To display your crontab file

crontab -l

root can view any users crontab file by adding “-u username”

crontab -u bappy -l  # List bappy's crontab file.

* * * * * Command to be executed
- – – – -
| | | | |
| | | | +—– Day of week (0-6)
| | | +——- Month (1 – 12)
| | +——— Day of month (1 – 31)
| +———– Hour (0 – 23)
+————- Min (0 – 59)

Field Allowed values
—– ————–
minute 0-59
hour 0-23
day of month 1-31
month 1-12 (or names, see below)
day of week 0-7 (0 or 7 is Sun, or use names)

To edit crontab file

crontab -e

#change the editor used to edit file set the EDITOR environmental variable like this:

export EDITOR=/usr/bin/emacs