Know how that i want to learn but i dont know where should i get it

Directories

1. [[bin|/bin]] — user commands (often a symlink to /usr/bin)
2. [[boot|/boot]] — kernel, initramfs, bootloader
3. [[dev|/dev]] — device files (disks, terminals, /dev/null)
4. [[etc|/etc]] — system-wide configuration
5. [[home|/home]] — users' personal files and dotfiles
6. [[lib|/lib]] — shared libraries and kernel modules (often a symlink to /usr/lib)
7. [[lib64|/lib64]] — 64-bit libraries and the dynamic loader (often a symlink into /usr)
8. [[media|/media]] — removable media mount points
9. [[mnt|/mnt]] — temporary manual mounts
10. [[opt|/opt]] — self-contained third-party apps
11. [[proc|/proc]] — live process and kernel info (virtual)
12. [[root|/root]] — root user's home
13. [[run|/run]] — runtime data since boot (PIDs, sockets)
14. [[sbin|/sbin]] — admin commands (often a symlink into /usr on modern systems)
15. [[srv|/srv]] — data served by this machine
16. [[sys|/sys]] — live hardware and driver info (virtual)
17. [[tmp|/tmp]] — temporary files, wiped on reboot
18. [[usr|/usr]] — installed software, read-only data
19. [[var|/var]] — changing data: logs, caches, databases

Topics

• [[networking|Networking]] — interfaces, IP and routing, DNS, network manager, ports, firewall, tools
  • [[interfaces]] · [[ip-routing]] · [[dns]] · [[network-manager]] · [[sockets-ports]] · [[firewall]] · [[tools]]
• [[systemd|Systemd]] — PID 1, units, services, timers, logs, boot
  • [[units]] · [[services]] · [[timers]] · [[journal]] · [[targets-boot]] · [[user-units]] · [[systemctl-cheatsheet]]
• [[users|Users]] — UID/GID, managing users, groups, sudo/su, login sessions, PAM
  • [[uid-gid]] · [[user-management]] · [[groups]] · [[sudo-su]] · [[login-sessions]] · [[pam]]
• [[permissions|Permissions]] — rwx, special bits, umask, ACLs, attributes, capabilities, SELinux/AppArmor
  • [[file-permissions]] · [[special-bits]] · [[umask]] · [[acl]] · [[attributes]] · [[capabilities]] · [[mac-selinux-apparmor]]
• [[processes|Processes]] — lifecycle, process tree, job control, signals, trap, priority, limits
  • [[process-lifecycle]] · [[process-tree]] · [[job-control]] · [[signals]] · [[sending-signals]] · [[trap]] · [[priority-scheduling]] · [[resource-limits]]
• [[storage|Disks & filesystems]] — block devices, partitions, filesystems, mounting, disk usage, btrfs, LVM/RAID/LUKS, swap, disk health
  • [[block-devices]] · [[partitions]] · [[filesystems]] · [[mounting]] · [[disk-usage]] · [[btrfs]] · [[lvm-raid-luks]] · [[swap]] · [[disk-health-io]]

Important files

[[files|All important files]] — one note per file (passwd, shadow, fstab, sudoers, hosts, /dev/null, .bashrc, config.fish, ...)

Where do I find ...?

I'm looking for ...	Look in
A program / command	[[usr]] /usr/bin, ~/.local/bin, [[opt]]
Where a command comes from	which cmd, type -a cmd, readlink -f $(which cmd)
A shared library (.so)	[[usr]] /usr/lib, ldconfig -p
System config	[[etc]]
My app config	[[home]] ~/.config
Default config shipped by package	[[usr]] /usr/lib, /usr/share
Logs	[[var]] /var/log, journalctl
Disks and partitions	[[dev]] /dev/nvme*, /dev/disk/by-uuid, lsblk
Mounted drives / USB sticks	[[run]] /run/media/$USER, [[mnt]], findmnt
Running process info	[[proc]] /proc/<pid>
CPU / memory / load	[[proc]] /proc/cpuinfo, /proc/meminfo, /proc/loadavg
Hardware: temps, battery, network card	[[sys]] /sys/class/*
Kernel settings (live)	[[proc]] /proc/sys, [[sys]]
Kernel settings (permanent)	[[etc]] /etc/sysctl.d, /etc/modprobe.d
Kernel + bootloader	[[boot]]
Kernel modules	[[lib]] /lib/modules/$(uname -r)
systemd units	[[usr]] /usr/lib/systemd/system, [[etc]] /etc/systemd/system
Caches / program state data	[[var]] /var/cache, /var/lib
Sockets, PID files	[[run]]
Temporary files	[[tmp]], [[var]] /var/tmp
Man pages, icons, fonts, .desktop files	[[usr]] /usr/share