Linux File System Basics
Part of the Linux All-in-One For Dummies Cheat Sheet
To interact with the Linux file system, you must understand some basics: its key directories, some of the most commonly used commands, and the permissions you can assign to files.
Key directories in the file system:
*/: Root directory (base of file system)
/bin: Executable programs
/boot: Linux kernel and boot loader
/dev: Special device files
/etc: System configuration files
/home: Home directories of all users
/lib: Library files for programs
/media: Mount points for CD-ROM and other media
/root: Home directory of the root user
*/sbin: System administration commands
/srv: Data for services such as Web and FTP
*/tmp: Temporary directory
/usr: Many of the important administration programs
/var: Various system files, such as logs
cat: Copies a file to the standard output
cd: Changes the current directory
chmod: Changes file permissions
chown: Changes file ownerships
cp: Copies files
dd: Copies blocks of data
df: Reports disk space usage by device and available space
diff: Compares two text files
du: Reports disk space usage by directory
file: Displays the type of data in a file
find: Finds files based on specified criteria
grep: Searches for text in a file
ln: Links a filename to an alias name
ls: Displays the contents of a directory
mkdir: Creates a directory
more: Displays a text file, one page at a time
mount: Mounts a file system
mv: Renames or moves a file
pwd: Displays the current directory
rm: Deletes files
rmdir: Deletes directories
sort: Sorts lines in a text file
split: Splits a file into smaller parts
umount: Unmounts a file system
wc: Counts the words and lines in a file
rwxrwxrwx: Three sets of rwx. The leftmost set pertains to the owner, the middle set is for the group, and the rightmost set is for others; rwx stands for read (r), write (w), execute (x); the dash (-) means no permission.
rwx------: Only the owner can read, write, and execute.
rw-r--r--: Everyone can read, and the owner can also write.
rw-------: Only the owner can read and write.
r--r--r--: Everyone can read.
Permissions can also be expressed numerically, where read (r) is equal to 4, write (w) is equal to 2, execute (x) is equal to 1, and no permission is equal to 0. Therefore, rwxrwxrwx is equal to 777, rwx------ is equal to 700, rw-r--r— is equal to 644, rw------- is equal to 600, and r--r--r-- is equal to 444.