Ubuntu Command

Linux overview#

Many other distribution on many bases was publication. But I mostly focus on:

RPM-based:

• Use .rpm file format
• Represent:
  • CentOs <- Redhat enterprise Linux
  • Fedora
  • openSUSE
  • apt-rpm
  • ....

Debian-based:

• Emphasizes free software.
• .deb package format and the dpkg package manager and its frontends (such as apt or synaptic).
• Represent:
  • Ubuntu (version xx.04 are LTS)
  • Debian
• Basically deb file was prettumuch equivalent to msi setup file. And instead of double click to install, we do command line sudo apt install [path to the file]

General file structure

LINUX DEBIAN BASED

File Structure:

• /bin: Binary files for single user
• /sbin: [System Binary files] Binary files for multiple users (for all users sessions mode).
• /boot: Linux image and boot configurations files
• /dev: pseudo files representing devices (such as mouse, keyboard, printer,...)
• /etc: configuration files use be system
• /home: user's files
• /lib: software library dependencies
• /root: root user's files
• /usr: non-essential addition binaries
• /var: files that would be update frequently (logs, application data, cache,...)

Pseudo files directories: Files that got dynamic generated, not persistence, by system boot or some event.

• /proc: Files representing running system processes
• /dev: as upper section
• /sys: Data on system and kernel resources

Create window usb installation#

• Using WoeUSB, download bash file as tutorial
• Install wimtools via sudo apt-get install wimtools
• Plugin USB, find device by sudo fdisk -l
• Run the script, e.g. sudo ./woeusb-5.2.4.bash -d ./Win11_English_x64v1.iso /dev/sda

Shortcut#

• Ctrl+Alt+T: Open terminal
• Ctrl+H: Show/hide hidden files

Command#

Woking with system#

• Listing what packages are installed on Ubuntu Linux
• landscape: Show useful current status of machine (SysInfo: each integer represent approximately 1 CPU full run)
• sudo setfacl -R -m u:[UserName] :rwx /app
  • setfacl: Sets Access Control Lists (ACLs) of files and directories.
  • R: Recursive
  • m: Modify
  • rwx: read write exucute permission
  • /app: directory
• chmod: The command sets the file permissions flags on a file or folder. The flags define who can read, write to or execute the file. r: read - w: write - x: execute -R: recursive -m: modify +x: add executable type to the file, usually the .sh files
• sudo ufw status: firewall status of machine
• which [binary]: trace the binary location in the system file structure
• sudo apt install [things we want to install] - sudo apt install nginx: install nginx
  • apt: ubuntu package management, equivalent to npm of node and maven of java. apt is basically a tool merges functionalities of apt-get and apt-cache. Favor apt over the other two if possible.
• systemctl status [process name]: Get process information
• sudo systemctl start [service file]: Execute the service file
• sudo systemctl stop nginx: stop nginx
• sudo apt purge nginx
• sudo apt-get autoremove
• sudo systemctl deamon-reload
• sudo systemctl restart nginx

User and Group#

• sudo useradd -m [userName]: -m create a folder in home tree directory with the user's name
• sudo passwd [userName]: change specific user password
• sud groupadd [groupName]: create a new user group
• sudo chown :[groupName] [absolutePath]: grant owner permission to user group following the absotule path
• sudo usermod -a -G [groupName] [userName]: Modify user permission
  • -a: add
  • -G: Existing group, normally followed by group name and user name
• sudo chmod g+w [absolutePath]: Add write permission of the [absolutePath] to the user group.

File Manage#

• du: Check how much space a file or a directory takes(Disk Usage).
• df: Shows the size, used space, and available space on the mounted filesystems of your computer.
• find: Track down files that you know exist if you can’t remember where you put them.
• locate: Locate a file, just like the search command in Windows.
• ls: It lists the files and folders in the directory you specify. By default, ls looks in the current directory.
  • -a: All, include hidden files
• pwd: Prints the working directory (the current directory) from the root / directory.
  
• mkdir: Allows you to create new directories in the filesystem. You must provide the name of the new directory to mkdir.
• cp: Use the cp command to copy files from the current directory to a different directory.
• mv: Allows you to move files and directories from directory to directory. It also allows you to rename files.
• rm: Delete directories and the contents within them.
  
• tar: Create an archive file (also called a tarball) that can contain many other files. This makes it much more convenient to distribute a collection of files.
• zip, unzip: Use the zip command to compress your files into a zip archive, and use the unzip command to extract the zipped files from a zip archive.
• gzip: Compresses files.

File Interactive#

• cat: Concatenate lists the contents of files to the terminal window. This is faster than opening the file in an editor, and there’s no chance you can accidentally alter the file
• diff: Compares two text files and shows the differences between them.
• grep: Searches for lines which contain a search pattern. Could be consider as small version of regex.
• head: Gives you a listing of the first 10 lines of a file. If you want to see fewer or more lines, use the -n (number) option.
• tail: Gives you a listing of the last 10 lines of a file.
• less: Allows you to view files without opening an editor. It’s faster to use, and there’s no chance of you inadvertently modifying the file
• touch: create a file

Common Operations#

• echo: Prints (echoes) a string of text to the terminal window.
• man: The man command displays the “man pages” for a command in less . The man pages are the user manual for that command.
• history: Lists the commands you have previously issued on the command line.
• ps: Lists running processes
• free: Gives you a summary of the memory usage with your computer. It does this for both the main Random Access Memory (RAM) and swap memory. -h: human is used to provide human-friendly numbers and units
• top: Shows a real-time display of the data relating to your Linux machine. The top of the screen is a status summary. Press the Q key to exit from top.
• uname: Obtain some system information regarding the Linux computer you’re working on.
• hostname: know the name of your host/network.
• jobs: Display all current jobs along with their statuses. A job is basically a process that is started by the shell.
• shutdown: Shut down or reboot your Linux system. Using with no parameters will shut down your computer in one minute.
• exit: Close a terminal window, end the execution of a shell script, or log you out of an SSH remote access session.
  
• ssh: Make a connection to a remote Linux computer and log into your account.
• cd: The cd command changes your current directory. In other words, it moves you to a new place in the filesystem.
• sudo: Required when performing actions that require root or superuser permissions, such as changing the password for another user.
• whoami: Find out who you are logged in as or who is logged into an unmanned Linux terminal.
• w: Lists the currently logged in users.
• apt-get: Command used to install and update packages - Favor apt more over if possible.
  
• finger: Gives you a short dump of information about a user, including the time of the user’s last login, the user’s home directory, and the user account’s full name.
• groups: Tells you which groups a user is a member of.
• useradd: To create a new user.
• userdel: To delete the users account.
• passwd: Lets you change the password for a user. Just type passwd to change your own password.
  
• chown: Allows you to change the owner and group owner of a file.
  
• kill: The kill command allows you to terminate a process from the command line. You do this by providing the process ID (PID) of the process to kill.
• wget: Download files from the internet.

Un-classified command#

• man [name of command]: provide user manual of the specific command.
• #![absoluteAddressToTheBinaryFile]: Tell linux the file is the executable script, and will run base on the Binary File.

Install SSH#

• On server: apt install openssh-server
• On client: apt install openssh-client
• /etc/ssh:
  • sshd_config: edit system host behavior
  • ssh_config: handle the way your system will login as a client on remote hosts
• ssh [user]@[serverIpAddress]
  • user: the user we want to use to login when use ssh
  • serverIpAddress: Ip of the server we want to connect
• scp [localfile] [user]@[serverIpAddress]:[absolutePathOnTheServer]: securely copy a file from local machine to the server

Common Parameters#

• -a: All
• -l: long form
• -h: human readable format
• -t: order by descending chronological order
• xzf: Extract zip file
• czf: Compress zip file

Furthur investigation#

• systemd
• Many options that can pass-in when run an asp.net core application. Sample: dotnet [appName].dll --url http://*:5000 (run appName, Kestrel listen http on port 5000)
• ip addr: Show network information
• netstat -ant: trace network currently running -l: Listing all listsening port
• host [domain website name]: give the public ipaddress of the site
• etc/hosts: the place you can config your own ip-mapping on the machine

Common task#

Run a script at boot-time#

#!/bin/sh -e
#
# rc.local
#
# This script is executed at the end of each multiuser runlevel.
# Make sure that the script will "exit 0" on success or any other
# value on error.
#
# In order to enable or disable this script just change the execution
# bits.
#
# By default this script does nothing.

exit 0

• The commands are run under root user.
• Place commands above the line that says exit 0.
• Make it executable by chmod +x /etc/rc.local.
• If the file is not exists yet, create it nano /etc/rc.local.