Linux Useful Commands / Features

For ease of access i want to put some of my day-to-day most useful commands in one place,
Off course share it with anyone who needs it.

Start with a quick and simple tool to verify weather a device is listening on some port/ports - NETCUT

# nc [option] [destination IP / hostname] [port]
to scan udp port use option '-zu'
to scan tcp port use option '-zt'
for list of options use just '-h'
for example :
# nc -zu google-public-dns-a.google.com 53
Output will be
Connection to google-public-dns-a.google.com. 53 port [udp/domain] succeeded!
# nc -zt google.com 80-81
Output will be
Connection to google.com 80 port [tcp/http] succeeded!
notice that non-responsive ports will not bring any output.

Create a file by size, may be useful for speed, latency or bandwidth testing

# dd if=/dev/zero of=<File Name>  bs=<Size>  count=<Multiplayer># dd if=/dev/zero of=output.dat  bs=1024  count=100240Output will be100240+0 records in100240+0 records out102645760 bytes (103 MB) copied, 0.494406 s, 208 MB/s

I'll add mode commands further on..

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