Debian

Journalctl

$  journalctl -b 

lid swicth

$  nano /etc/systemd/logind.conf 

 HandleLidSwitch=ignore 
 HandleLidSwitchExternalPower=ignore 
 HandleLidSwitchDocked=ignore 

$  systemctl restart systemd-logind 

Show all established connections

$  lsof -i| grep ESTABLISHED 

Listing Running Services

List all loaded services on your system

$  systemctl 
$  systemctl list-units --type=service 
$  systemctl --type=service 

List all loaded but active services

$  systemctl list-units --type=service --state=active 
$  systemctl --type=service --state=active 

Get a quick glance of all running services

$  systemctl list-units --type=service --state=running 
$  systemctl --type=service --state=running 

Stop, Disable service

$  systemctl stop [servicename] 
$  systemctl disable [servicename] 
$  rm /etc/systemd/system/[servicename] 
$  rm /etc/systemd/system/[servicename]  and symlinks that might be related
$  rm /usr/lib/systemd/system/[servicename]  
$  rm /usr/lib/systemd/system/[servicename]  and symlinks that might be related
$  systemctl daemon-reload
$  systemctl reset-failed

netstat

$  netstat -tlnp 
$  netstat -lnp 

Ports

Listing of every port available

$  less /etc/services 

Locate listening ports

$ ss -tulwn | grep LISTEN 

Kill process running on port ***

$ kill -9 `sudo lsof -t -i:3002` 

User

To add user
adduser username

You can use the following command:

$ useradd -r subversion

-r, --system                  create a system account

The -r flag will create a system user - one which does not have a password, a home dir and is unable to login.

For more info, check manual pages with this command:

$ man useradd

You will find in this documentation the following flag that can be used for your purpose.

You can use the -M switch (make sure it's a capital) to ensure no home directory will be created:

$ useradd -M subversion

then lock the account to prevent logging in:

$ usermod -L subversion

This isn't a particularly strong answer, the user created by this means still has a shell. And you did not even warn the OP that this was the case. Retrospectively that would be usermod -s /bin/false subversion, or with --shell /bin/false to useradd 

$ usermod user --shell /bin/false

To delete the user, without removing the user files, run:

deluser username

If you want to delete the user and its home directory and mail spool, use the --remove-home flag:

deluser --remove-home username

Network

$  /sbin/ifup eth0 
$  /sbin/ifdown eth0 
$  ip addr flush dev eth0 
$  /etc/init.d/networking restart 
$  /etc/init.d/networking stop
$  /etc/init.d/networking start
$  systemctl restart networking
$  systemctl status networking.service