Linux Essentials Preparation · lesson 6 of 23 · 25 min
The FHS (Filesystem Hierarchy Standard)
Linux uses a single unified directory tree starting at / (root). All files and devices are accessible from this root. The FHS (Filesystem Hierarchy Standard) defines the purpose of each top-level directory.
File types in Linux: Regular file (-), Directory (d), Symbolic link (l), Block device (b), Character device (c), Named pipe (p), Socket (s). Shown in the first character of ls -l output.
/proc filesystem: Virtual — not on disk. Contains process information (/proc/PID/), system info (/proc/cpuinfo, /proc/meminfo), and kernel parameters (/proc/sys/).
/dev/null — discards all data written to it. /dev/zero — produces infinite null bytes. /dev/random — produces random bytes.
Exam Tip
Know the purpose of each top-level directory. /etc = config files. /var/log = log files. /proc = virtual kernel info. /tmp = cleared on reboot. /home = user directories. /boot = kernel and bootloader.
Key Terms
Key Terms
Knowledge Check — 8 Questions
Linux Essentials — Filesystem Hierarchy
System configuration files are stored in:
- /bin
- /etc
- /var
- /usr
- Answer: /etc
/etc contains system-wide configuration files — sshd_config, passwd, fstab, hosts, resolv.conf, etc. Log files are typically stored in:
- /tmp
- /proc
- /var/log
- /etc/log
- Answer: /var/log
/var/log contains system and application logs — auth.log, syslog, kern.log, apache2/, nginx/, etc. /proc is described as a virtual filesystem because:
- It is encrypted
- It is not stored on disk — it represents kernel and process data in memory
- It is read-write only
- It stores temporary files
- Answer: It is not stored on disk — it represents kernel and process data in memory
/proc is generated dynamically by the kernel — reading /proc/cpuinfo gives real-time CPU info without reading a file on disk. The /tmp directory is:
- Permanent storage for temp files
- Cleared on reboot
- Only accessible by root
- Used for device files
- Answer: Cleared on reboot
/tmp is for temporary files — cleared on reboot. Applications use it for scratch space. Do not store important data here. The kernel and bootloader files are stored in:
- /etc
- /boot
- /usr
- /lib
- Answer: /boot
/boot contains the kernel (vmlinuz), initramfs, and GRUB bootloader files needed to start the system. Writing data to /dev/null:
- Saves it to a null file
- Discards it permanently
- Sends it to /tmp
- Encrypts it
- Answer: Discards it permanently
/dev/null is the “black hole” — anything written to it is discarded. Used to suppress output: command 2>/dev/null. User home directories are located under:
- /root
- /home
- /usr
- /var/home
- Answer: /home
/home contains subdirectories for each regular user (/home/alice, /home/bob). The root user’s home is /root.
The root of the Linux filesystem is represented by a single _____ character.
Answer: /
The Linux filesystem starts at / (forward slash) — the root directory. All other directories are subdirectories of /.
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