1. host
If you need to find out the IP of a domain, type
host apple.de
apple.de has address 17.172.224.31
apple.de has address 17.149.160.31

2. whois
You can use whois to quickly find if a domain name exists and its registrar information.
whois apple.com
[Querying whois.verisign-grs.com]
[whois.verisign-grs.com]
Whois Server Version 2.0
Domain Name: CLOUDSY.COM
Registrar: ENOM, INC.
Whois Server: whois.enom.com
Referral URL: http://www.enom.com
Name Server: NS1.CLOUDSY.COM
Name Server: NS2.CLOUDSY.COM
Status: ok
Updated Date: 28-mar-2009
Creation Date: 25-mar-2009
Expiration Date: 25-mar-2010

3. passwd
If your web host gave you SSH access, you can use it to do simple things in your account like quickly changing your password.
passwd yourusername
Changing password for user yourusername.
New UNIX password:
Retype new UNIX password:
passwd: all authentication tokens updated successfully.

4. cd – Navigate to your Desktop
cd /users/yourusername/Desktop
Navigate in a web server
cd /home/yourusername/public_html/site
5. mkdir – Make a new directory
mkdir Photos
6. mv – Move a file into a folder
mv IMG_8151.JPG Photos

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