Basic Linux System Tools and Configuration

Basic Linux System Tools and Configuration
(posted 2018.12.01, last updated 2018.12.14)

Tested for Ubuntu 18.04

Useful Packages/Tools

/etc/hosts

  127.0.0.1       localhost
  127.0.1.1       server1.example.net

/etc/hostname
```
  server1.example.net
```
Helpful commands
Test SSH config without restarting
sshd -t
Check open ports
netstat -tulpn
Detailed information about specific open port
lsof -t -i :8000 | xargs ps -fp
Rsync
rsync -av --exclude 'somefolder' --delete --usermap=userSrc:userTgt -groupmap=grpSrc:grpTgt -e "ssh -p 4224" /var/source/ root@example.net:/var/source
Screen
- screen -R reattaches a screen if available or creates a new one. To disconnect (not closing a screen) press CTRL+a then d

- Open `/etc/default/motd-news` 
- Set `ENABLED=0`

nano /etc/pam.d/common-session-noninteractive
Add session [success=1 default=ignore] pam_succeed_if.so service in cron quiet use_uidsession [success=1 default=ignore] pam_succeed_if.so service in cron quiet use_uid in front of session required pam_unix.sosession required pam_unix.so.
Restart cron service cron restart