Linux basics for hackers
In this article i will introduce you the book “linux basics for hackers”. I will not dug deeper and just copy-paste this amazing book, I’ll use this as a way to memorize better the concepts and core arguments.
Important therms
- Binaries: this term refers to file that can be executed, like windows .exe files. They generally reside in the usr/bin or user/sbin folders (examples: ps, cat, ls, ifconfig, google…).
- Linux is case sensitive: desktop is different from Desktop
- Home: Every user has a home directory
- Root: administrator privileges
- Shell: an environment and interpreter for running commands on linux. The most used is called bash
Linux Filesystem
![](/assets/filesystem.jpeg)
the Linux filesystem is structured as if it were an upside down tree, the top is called root (/): here are some of the most important:
- /root: home dir of root user
- /etc: it generally contains Linux config files
- /home: user home directory
- /mnt: where other filesystem are connected or mounted
- /media: where CD and USB are mounted into the filesystem
- /bin: where binaries reside
- /lib: where I’ll find libraries (shared programs that are similar to windows DDLs)
basic commands
- pwd: (print working directory)
- whoami
- cd
- ls
- man (command info)
- locate (file location)
- whereis (find a binary)
- which (shows search result query from PATH variable)
- find (the most powerful for searching, You can do a deeper scan with other parameters like creation date)
- grep (can be used as a filter to search for keywords)
- ps (used to find and display info about running processes)
Modifying files and directories
- cat (generally used for dispaying the contents of a file but it can olso create a file)
- touch (edit or create a file)
- mkdir (create a directory)
- cp oldfile /root/folder/newfile (copy a file in a new destination)
- mv filename filename2 (move command as the same concept as cp, it can also rename a file)
- rm (remove a file)
- rmdir (remove a directory)
redirect character (>)
file creation with cat example:
cat > helloworld.txt
#interacrive mode: "hello"
when you press enter, Linux will go in interactive mode, you can now write content to that file. To exit just press ctrl-d
append character (»)
cat >> helloworld.txt
#interactive mode: " world!"
You’ll be prompted to the interactive mode again
final result
cat helloworld.txt
hello world!
for overwriting you can use again the “>” character