Xorg, Wayland, XWayland
Window Managers, X Compositors, Desktop Environments
Freetype Font Renderer
xinitrc, xsession, startx
ALSA, V4L2, pulseaudio, JACK, pipewire
XDG-Autostart, XDG Base Specifications (Freedesktop Specifications, Formerly XDG)
LSB Filesystem Heirarchy Specification
fstab, mount, mkfs, parted, fdisk, fsck, btrfs-progs, chroot, ifconfig, iptables, dd, tar
External Programs: ss, ps, pstree, dig, 7z
Processes, Daemons, Buses, Sockets, Addresses, Ports, IPC
Firewall, SELinux, AppArmor
Users, Groups and File Permissions
OS Specific: Package Management
D-Bus, udisks, gvfs, fuse, udev (systemd-udevd/eu-udev), logind (systemd-logind/elogind), Polkit
grub, efibootmgr, initramfs, vmlinuz
Video Drivers, Kernel Modesetting, DRM, Mesa, OpenGL, Vulkan
Credential Managers: GNOME Keyring, KDE Wallet

Basic GUI Apps:
File Managers (Nautilus, Nemo, Dolphin, Thunar)
Package Manager Frontends (Software Center, Discover, Pamac, YaST)

Developent Knowledge

GUI Frameworks: Qt, GTK
Static Link Libraries, Dynamic Link Libraries, Build Systems, Build Configurations, Compilers
Assembly, Processors, Logic Gates, Boolean Algebra
Containers, Virtual Machines, Emulators, VT-x/AMD-V
Cryptography, RSA, ECDSA, Blowfish, GPG, PGP

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