cheats/linux.md

# Linux Cheats

## 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`


## 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")

---
## 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 {} +`

---
## 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)


## 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`