====== Linux Basics ======

===== Boot =====


  - BIOS/UEFI
  - SHIM
  - GRUB
  - KERNEL
  - Init process / process 0
    * systemd
  - User Space 
    * Windows manager


===== Folder =====

  * /bin/
    * binaries, sbin: superuser binaries
  * /boot/
  * /dev/
    * devices
  * /etc
  * /home/
  * /media/
  * /mnt/
  * /opt/
  * /proc/
  * /root/
  * /run/
  * /srv/
  * /sys/
  * /usr/
  * /var/

===== File/Folder permissions =====

| type | [special] ||| owner ||| group ||| all ||| 
| d,-,l | SUID | SGID | Sticky |r | w | x | r | w | x | r | w | x | 
| | 4 | 2 | 1 | 4 | 2 | 1 | 4 | 2 | 1 | 4 | 2 | 1 |

===== File types =====

  * First four bytes ('Magic Bytes') define file type



===== IPC =====

| 1 | sighup | stop terminal connection |
| 2 | sigint | interrupt terminal connection |
| 9 | sigkill | |
| 15 | sigterm | |
| 18 | sigcont | |
| 19 | sigstop | |