cheats/linux.md

# Linux Cheats

## General (tested in Debian)

### Set script as startup
If, for some reason, apache isn't startup:

> `sudo update-rc.d apache2 defaults`

### Check a package version/info
> `dpkg -l matrix-synapse`

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### Installing from tar.gz
Pure binaries:

> `sudo tar --directory=/opt -xvf <file>.tar.[bz2|gz]`     
> add the directory to your path: `export PATH=$PATH:/opt/[package_name]/bin`     

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## SSH
Copy files to/from an SSH connection: (SSH format: `user@host:/path` )
> `scp <source> <destination>`

Recursivly give directories execute privileges: (`-type f` for files instead)
> `find /path/to/base/dir -type d -exec chmod +c {} +`

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## GROUPS
Create groups
> `groupadd <groupName>`

Add user to a group
> `usermod -a -G <group> <user>`

### Open ports with iptables

Don't do that. Use [UFW](https://www.digitalocean.com/community/tutorials/how-to-set-up-a-firewall-with-ufw-on-debian-10) instead.

Allow a connection with UFW:
> `sudo ufw allow <port/service>`

Enable ufw service:

> `sudo ufw enable`

+ [Source](https://www.linuxquestions.org/questions/linux-security-4/how-to-open-ports-with-iptables-237939/)
+ [Source2](https://www.digitalocean.com/community/tutorials/iptables-essentials-common-firewall-rules-and-commands)

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### Partitions
The following command is not permanent:
> `mount /dev/sda11 /opt`

To mount partition permanently, instert the following into `/etc/fstab`:
> `UUID=03ec5dd3-45c0-4f95-a363-61ff321a09ff /opt ext4 defaults 0 2`

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## Arduino
Find what 'channel'(?) the Arduino is plugged in at:
`dmesg | grep tty`

Do following commands to "talk" with an Arduino (with a set script):
> python    
> import serial    
> ser = serial.Serial('/dev/ttyACM0',115200)    
> ser.readline()    
> ser.write("PP\n")    

To set the time of current clock-program, continue with:
> `from datetime import datetime`    
> `ser.write("T"+datetime.now().strftime("%y%m%d0%w%H%M%S")+"\n")`    
> `ser.readline()`