In this lession we will learn about the file system of the Unix
In Unix/Linux everything is organized as file. Unix/Linux follows a Filesystem Hierarchy Standard which defines how the directories in the Unix should be organized.
Lets go to root directory
Now here in root if you do pwd then you should be able to see following
Now here if you list files you should get following directories
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| $ ls
bin cdrom etc lib lib64 lost+found mnt proc run snap sys usr
boot dev home lib32 libx32 media opt root sbin srv tmp va
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We can also use the tree command with depth option set to 1 using -L option to see the directories in the / as shown below
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| dbit@Tayyabali:/$ tree -L 1
.
├── bin -> usr/bin
├── boot
├── cdrom
├── dev
├── etc
├── home
├── lib -> usr/lib
├── lib32 -> usr/lib32
├── lib64 -> usr/lib64
├── libx32 -> usr/libx32
├── lost+found
├── media
├── mnt
├── opt
├── proc
├── root
├── run
├── sbin -> usr/sbin
├── snap
├── srv
├── sys
├── tmp
├── usr
└── var
24 directories, 0 files
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Now lets go through all these directories and their usage in the Unix envirnment
This is on the top of the directory root, from here everything starts, we can go to this root by simply changing to using cd /
/boot#
Lets see in the boot directory
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| $ /boot ls
config-5.13.0-27-generic memtest86+.bin
config-5.13.0-28-generic memtest86+.elf
config-5.13.0-30-generic memtest86+_multiboot.bin
efi System.map-5.13.0-27-generic
grub System.map-5.13.0-28-generic
initrd.img System.map-5.13.0-30-generic
initrd.img-5.13.0-27-generic vmlinuz
initrd.img-5.13.0-28-generic vmlinuz-5.13.0-27-generic
initrd.img-5.13.0-30-generic vmlinuz-5.13.0-28-generic
initrd.img.old vmlinuz-5.13.0-30-generic
lost+found vmlinuz.old
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This directory stores
+ Boot files are used to boot the computer, usually kernel files, temporary file system
+ These files belong to grub boot loader
+ Usually needed before the user programs start executing
+
/bin#
Lets move to /bin and see whats inside this directory
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| $ cd bin/
$ ls
'[' mcomp
aa-enabled mcookie
aa-exec mcopy
aclocal md5sum
aclocal-1.16 md5sum.textutils
aconnect mdel
acpi_listen mdeltree
add-apt-repository mdig
addpart mdir
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/bin contains the binary executable files which are commonly used.
/dev#
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| $ cd /dev/
$ ls
acpi_thermal_rel i2c-7 null tty21 tty6 uhid
autofs i2c-8 nvme0 tty22 tty60 uinput
block i2c-9 nvme0n1 tty23 tty61 urandom
btrfs-control initctl nvme0n1p1 tty24 tty62 userio
bus input nvme0n1p2 tty25 tty63 v4l
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In this directory we get all device files. In Linux based system all devices are considered as a files.
/etc#
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| $ cd /etc/
$ ls
acpi hostid polkit-1
adduser.conf hostname popularity-contest.conf
alsa hosts ppp
alternatives hosts.allow profile
anacrontab hosts.deny profile.d
ansible hp protocols
apache2 ifplugd pulse
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All files are under this directory are the configuration files. You can change the variables in these file to configure the setting of the entire system.
/home#
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| $ cd /home/
$ ls
dbit lost+found ubuntu
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This directory is home for all users home directory. As you can see above we have dbit and ubuntu home directories for dbit and ubuntu users. lost + found is directory which stores the files which are not referenced or files not saved and system crashed becouse of power failure or any other kind of problems.
/lib#
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| $ cd /lib
$ ls
accountsservice libpdal_plugin_writer_sqlite.so.10
apg libpdal_plugin_writer_sqlite.so.9
apparmor libpdal_util.so.10
apt libpdal_util.so.9
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/lib contains the libraries used by the system. You wil find .so file extensitions if these files, these are dynamically linked libraries.
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| $ cd /media/
$ ls
dbit
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Here you will find the externally mounted deviced like hard disks, CDs etc
/mnt#
This is also same as /media but here we mount file system temporary like network file systems
/opt#
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| $ cd /opt/
$ ls
google openboard zoom
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Here we have all the softwares which are additionally installed like databases.
/sbin#
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| $ cd /sbin
$ ls
aa-remove-unknown grub-macbless pppdump
aa-status grub-mkconfig pppoe-discovery
aa-teardown grub-mkdevicemap pppstats
escapesrc mkntfs useradd
faillock mkswap userdel
fatlabel ModemManager usermod
fdformat modinfo uuidd
fdisk modprobe validlocale
filefrag mount.fuse vcstime
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/sbin stores binay files like /bin but here you will get all admin commands not commom user commands.
/tmp#
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| $ cd /tmp/
$ ls
config-err-CjFGnT
hsperfdata_dbit
insync1000.sock
mkdocs_6ym74aw8
pyright-7430-VeDfGK0ubjhI
pyright-7430-ZjS2QpXL5DkR
python-languageserver-cancellation
snap.snap-store
snap.telegram-desktop
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Here all the applications store their tempopary files. Usually these file gets deleted when your system is rebooted.
/usr#
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| $ cd /usr/
$ ls
bin include lib32 libexec local share
games lib lib64 libx32 sbin src
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Usually this directory contains the user programs, documentations and libraries that take good amount of space. On server we need to make it little larger.
/proc#
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| $ cd /proc/
$ ls
1 1649 2 217 41 6330 7314 8668 execdomains
10 166 20 2195 414 6331 7364 8689 fb
1075 1661 2004 2197 415 6332 7430 871 filesystems
1076 1665 20089 22 419 6333 7449 8723 fs
11 1669 2010 224 42 6334 7476 874 interrupts
1115 1672 20203 225 422 6335 761 8743 iomem
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/snap#
/snap stores files and folders installed using snap
Information of this directory is created dynamically by the operating system. It contains the information about the running processes and it also containts the information of the system like file system, interrupts etc
Each number here is representing the process and its information.