# Most Useful Ubuntu Commands

**1. Open Terminal :** 

To open a terminal use below key board shortcut

> ctrl + alt + T

**2. Clear Terminal **:

To clear terminal use below command

> clear

**3. Files / Folders:**

a. create a file
> touch filename

b. create a folder
> mkdir foldername

c. list files / folders
> ls

d. list hidden files / folders
> ls -a

e. list files / folders with details such as permissions, filesize etc., .
> ls -l

f. print file content on terminal.
> cat filename

g. To combine two files (file1 and file2) into one file (file3):.
> cat file1 file2 > file3

h. copy content of file1 to file2. (creates file2 if dosen't exist)
> cp file1 file2

i. move file1 to folder1. (we can use it for both folders also)
> mv file1 folder1

j. search a file for a string
> grep "string to be searched" filename

k. delete a file.
> rm filename

l. delete a folder (with all its sub folders). 
> rm -r foldername

**4. Search for a process by name :**

To search for a process running by name you can use the below command.

> ps aux | grep "process name"

**5. Search for a process by port :**

To search for a process running by port you can use the below command.

> lsof -i :port

**6. Top Command : 
**

It will list all the processes running with information like **task**, **memory**, **cpu** etc.,

> top

**7. User Privilege Commands :**

a. run command as root (run any command as root user)
> sudo 

b. open a root shell
> sudo -s

c. exit a root shell
> exit

d. change your password
> passwd 

**8. Firewall Commands :**

a. turn on the frewall
> ufw enable

b. turn of the frewall
> ufw disable

c. allow all connections by default
> ufw default allow

d. allow trafic on port
> ufw allow port

**9. Package Management Commands :**

a. refresh available updates
> apt-get update

b. upgrade all packages
> apt-get upgrade

c. install pkg
> apt-get install pkg

d. uninstall pkg
> apt-get purge pkg

e. remove obsolete packages
> apt-get autoremove

f. try to fix broken packages
> apt-get -f install

**10. Find Ip address :**

To find IP address use the below command.

> ifconfig