Essential Linux Commands & File System Structure

Linux File System Structure: An archive of Linux is associated with 3 parts: superblock, inode table, and data blocks.

Network Ports: To see the ports assigned to services.

Display Active TCP/IP Connections: netstat -a

User Management:

• Create password: passwd (user)
• Add user to group: usermod -g group_name
• Disable: 60001
• Enable: 60002

Practical Commands:

Add User: adduser

1. Change folder privileges: chmod
2. Check privileges: ls -de (see if you changed privileges)

1. Create a user: useradd newuser
passwd newuser
2. Create a directory: The command mkdir is used to create directories:
   mkdir mydirectory
3. Create a report: ps -aux >> reporte.txt
4. Directories associated with the user: -d dirname
5. Changing permission: chmod 744 file.txt /file.txt
6. Change owner: chown
   Entering as root: # chown [user] [folder] -R
7. Render a file in a loop: (File $i) touch (think file) for (i)
8. Create a task in crontab: (memory occupied by process memory space) $ [data]
9. Archive files: The tar command does two things:
   1. Package folders within a file
   2. Compress file

   The tar command syntax: tar -zcvf archivo_nuevo.tar.gz dirname

   Where:

   • -z: Compress the file using gzip
   • -c: Create a file
   • -v: Verbose mode, displays progress
   • -f: Filename

Commands:

Processor type: arch
Calculator: bc (use quit to exit)
Calendar: cal or cal [[month] year] (e.g., cal 2003)
View file contents: cat
Change attributes: chmod
Change file owner: chown
Go out of a directory: cd ..
Change directory: cd
Clear the screen: clear

Compare files: cmp
Compress files: compress
Compress files (keep original): compress -c
Decompress files: compress -d
Copy files: cp
Display the date: date

Report disk space: df
Disk usage summary: du
Text editor: ed (starts in command mode, use i for text mode)
Text editor: ex
Locate files: find
Display a witty quote: fortune
Free and used memory: free
Email summary: frm
Compress files: gzip
C compiler: gcc
C++ compiler: g++
Decompress files: gunzip
Output first lines of a file: head
Output first two lines: head -2
Print computer system name: hostname
User and group ID: id
Terminate a process: kill
Forcefully terminate a process: kill -9 (see ps)
Past users logged in: last
List files and directories: ls
List all entries: ls -all
Reverse order list: ls -r
List in columns: ls -c
Logout: logout
Login: login
Create a shortcut: ln -s
Email: e-mail
Command manual: man
Display info page by page: more (exit with q)
Batch file editing: sed (e.g., sed -n '500,600p' archivote)
Create a directory: mkdir
Display a file one screen at a time: more
Rename: mv
Mount CD-ROM: mount /dev/cdrom /mnt/cdrom
Mount floppy (msdos): mount /dev/fd0 -t msdos /mnt/fd0
Mount hard drive (FAT32): mount /dev/hda1 -t vfat /mnt/hda1
Mount hard drive (NTFS): mount /dev/hdb1 -t ntfs /mnt/hdb1
Mount zip disk: mount /dev/sda1 /mnt/sda1
Change password: passwd
Determine process number: ps (see kill)
Current directory: pwd
Delete files: rm
Remove directories: rmdir
Create empty file or update date: touch
Kill X applications: xkill
Unmount disks or drives: umount
Unmount CD-ROM: umount /dev/cdrom
Text editor: vi
Count lines, words, characters: wc
Who is in the system: who
Write to another user: write