10 May 2020
Linux file names are case-sensitive.
Folders are referred to as Directories (if you’re coming from Windows). There are no Local Disks in Linux, everything is stored in the root directory. However, you can mount different directories to different partitions or storage devices if you want.
The linux file system layout is defined in the FHS (Filesystem Hierarchy Standard). However, some linux distributions don’t really follow it exactly. Several directory structuring styles have also changed over the years.
/ - Root directory contains everything that is needed to run the
system. If the linux kernel is the brain, the root directory is akin
to the heart of the system.
/bin - Short for binary. Contains the most basic binaries
necessary for the system, are present here such as ls, cat, etc.
/sbin - System binaries. These are binaries that a system
administrator would use. A standard user won’t have access to this
directory without proper permissions.
Both the
/binand/sbindirectories contain the binaries that are necessary for running the system in single user mode.
/boot - Contains everything an os needs to boot. Better not touch
anything here.
/cdrom - legacy mounting point for CD ROMS. Might not be present
in all distros.
/dev - Devices live here. Hardware devices such as keyboard,
mouse, hard disks, etc are present. Disks are referred to by the
files sdx.
/etc - etcetera. This directory contains system wide configuration
files.
/lib, /lib32, /lib64 - libraries are stored here. Required for
different binaries.
/media, /mnt - Contains mounted drives such as hard disks, usb
drives, hard drives, etc. The /media directory is used in recent
distros to manage disk drives by the system. When manually mounting
something, use the /mnt and let the /media directory to be
managed by the os.
/opt - optional directory. Usually contains vendor provided
packages. You can place the applications that you created here.
/proc - contains information about system processes and resources.
You can also find information about cpu such as cat /proc/cpuinfo
and find out the uptmie of the system cat /proc/uptime.
/root - Home directory for the root user. Unlike a typical user,
it does not contain all the directories found inside a user’s home
directory. Note that, this resides outside the /home directory. You
need root permission to access files in this directory. Why is the
root directory present in /root and not in /home/root? The
answer is, so that the root user can access his/her home directory
even if the /home directory is mounted on another partition or
disk which may not be available.
/run - fairly new, found in recent distros. Its a tempfs
(temporary file system), which means everything present here resides
in the RAM. So everything is gone, when you shut down/reboot the
system.
/snap - [not standard] contains the Snap package management
related files and directories. This is found in Ubuntu and any
system that utilizes the snap packaging system.
/srv - Service directory. Service data is stored here for example
when you run a web server or a ftp server, you would want to place
your files or directories that you want to serve, here for the users
to access.
/sys - System directory. Present around for a long time. Its a way
to interact with the kernel. Similar to the /run directory in
that, this directory does not actually physically exist, it is
created evertime the system boots up.
/tmp - Temporary directory - Used by applications to store
temporary files here such as files in word processors that you are
currently editing, etc. Should be safe to delete stuffs from this
directory.
/usr - User application space. Applications used by the users are
stored here as opposed to /bin and /sbin which contains
applications for the system. Also known as “Unix System Resource”.
Applications present here are considered non-essential for the os to
function properly. Most program installed from source code will
usually end up in /usr/local directory. Larger programs might
install into the /usr/share directory. Installed source code will
go into /usr/src.
/var - Variable directory. Contains files and directories that are
expected to grow in size. For example /var/log contains the logs
for different applications, /var/crash contains crash logs,
/var/cache to store different cache items.
/home - Home directory for users. Each user has his/her own home
directory in the format /home/username. Contains all user related
data such as user specific configuration files, cache, etc.
/home/username/.themes and /home/username/.icons contain themes
and icons that are available to the current user. If you want to
save all your settings, this is the directory that you want to
backup. After upgrading or updating to a new system, restoring the
/home directory means that all your settings will stay as is even
if you reinstall applications.