Linux Administration
Users and groups
Adding an existing user to an existing group usermod -a -G theExampleGroup theExampleUser Chang...
Passwords
Use pwgen to generate ramdom passwords pwgen will generate easy to remember passwords # pwgen ...
SSH / SCP without known_hosts check
When we want to connect to a remote host using different credentials and we have automatic login ...
Ubuntu startup mode
Show current default target sudo systemctl get-default To start in multi-user mode (text mo...
Testing networking services
Netcat Testing networking services to troubleshoot communications can be easily done with netcat...
Services
Managing services with systemctl Start sudo systemctl start application.service Stop sudo sys...
Securely delete files and directories
Shred shred -zvu -n 3 fileToDelete Wipe wipe -rfi privateDirectory/* SRM (secure remove) srm...
rsync
https://serverfault.com/questions/529287/rsync-creates-a-directory-with-the-same-name-inside-of-d...
IPTables
Allow All Incoming HTTP sudo iptables -A INPUT -p tcp --dport 80 -m conntrack --ctstate NEW...
Mounting ISO images under FreeBSD
https://makandracards.com/jan0sch/13431-mounting-iso-images-under-freebsd
Console on serial port
Example using RedHat Linux 6.0 Using lilo bootloader Edit /etc/lilo.conf append="console=tty0 ...
Some useful commands
Here is how to join two files side by side in columns, delimited by ";" paste file1 file2 -d ";"...