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Directory
Purpose
/
The beginning of the filesystem; all directories are underneath this
/etc
System-wide application configuration
/home
User home directories
/root
The home directory for root (root doesn't have a directory under 
/home
)
/media
For removable media, such as flash drives
/mnt
For volumes that are intended to stay mounted for a while
/opt
Additional software packages 
(some programs are installed here, not as common)
/bin
Essential user binaries (
ls
, 
cp
, and so on)
/proc
Virtual filesystem for OS-level components
/usr/bin
A majority of user commands
/usr/lib
Libraries
/var/log
Log files

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Chapter 4
[
 111 
]
The 
/etc
 directory deserves some additional discussion, as you'll no doubt be 
working with it a lot. This directory, as mentioned in the preceding table, holds 
configuration files for applications that are intended to be respected system-wide. 
For example, if you're running the OpenSSH daemon on your server, you're 
listening for connections via port 22 by default. (Don't worry, we'll discuss these 
individual concepts in further chapters.) The 
configuration file for the OpenSSH 
server is located in the 
/etc/ssh
 directory. Since OpenSSH is a service that runs on 
the system as a background process, its configuration is stored in the 
sshd_config
 
file inside that directory. If you remove the package responsible for providing 
OpenSSH, the configuration is retained in that file (removing packages doesn't 
remove config files by default), so if you go to reinstall OpenSSH later, you'll have 
the same configuration the next time. If we want to wipe out the configuration while 
uninstalling a package, we can use the 
--purge
 option with the 
apt remove
 command 
to do so, as we saw in 
Chapter 3
, 
Managing Software Packages
.
Other directories of importance will be discussed as we progress through the topics 
in this book. Don't worry if some of this doesn't make sense right now; it will come 
with time. The main point here is that there are many directories, each having their 
own purpose. If you want to know the purpose of a particular directory, consult the 
FHS. If you're curious where you should place something on a server, also consult 
the FHS. But again, don't worry too much about doing research outside of this book, 
as we'll cover the necessary topics as we go along.
We now have a better understanding of the default filesystem layout, and the 
purpose for some common directories. In the next section, we'll explore how we can 
view the contents of files stored in those directories.