Linux Ask! is a Q & A web site specific for Linux related questions. Questions are collected, answered and audited by experienced Linux users.
Emulate telnet using nc
Answer:
Telnet is a very useful tool for connecting to remote server, such as SMTP. However, you can replace the command telnet by nc, with the exact functionality.
Example: Connect to the local SMTP server.
# nc localhost 25
What is the SMTP submission port 587?
Answer:
A lot of ISPs will block the port 25 for preventing users from sending spam emails. To send email if you use such ISPs, you need to use port 587.
Port 587 is the official port for sending email on mail submission agents (MSAs), as defined in RFC 2476
Block website access in Linux
Answer:
The simple way to block access to web site is to change the hosts file.
1. Open the hosts file
# sudo vi /etc/hosts
2. Change the content, such as...
0.0.0.0 microsoft.com
0.0.0.0 oracle.com
3. Save the file.
Compress and decompress file using 7zip
Answer:
7zip is a well known compression program if you need a very small file size, i.e. high compression ratio.
To install under Ubuntu/Debian:
# sudo apt-get install p7zip
To compress a file
# p7zip test.txt
To decompress a file
# p7zip -d test.txt.7z
How to completely uninstall a package in Ubuntu/Debian?
Answer:
To completely uninstall a package in Ubuntu/Debian, you can use the command below:
# sudo apt-get --purge remove PACKAGE
That's it.
