# Linux Commands

Description	Comands
System Info	`uname -acat /etc/*-release`
Update software `-y` assumes yes to all prompts	`sudo apt-get update -y`
Install software (Debian/Ubuntu) `-y` assumes yes to all prompts	`sudo apt-get install -y <PACKAGE_NAME>`
Uninstall software	`sudo apt-get --purge remove <PACKAGE_NAME>`
Show current file path	`pwd`
Show all files in current directory `-l` display as a list `-a` show hidden files `-F` show all directories with a / at the end, making them easier to see `-h` show directory sizes in human readable format `-R` list directories recursively `-t` sort by modification date in ascending order, means the higher will be come first `-S` sort by size `-i` displays Inode information `-o` shows owner of the files and directories but not the groups `<STRING_TO_MATCH>` used to only display files and directories matching the string This doesn't see to work correctly when used with `-a`	`ls -l` `ls -l <STRING_TO_MATCH>`
Show hidden files	`ls -la`
Create hard and soft links to files `-s` creates soft link	`ln <FILE1> <FILE2>` `ln -s <FILE1> <FILE2>`
Tree view of directories `-d` only show directories	`tree` `tree -d /`
Create, update the access, change, and modify times of files `-t` allows you to set the date and timestamp of the file to a specific value e.g. 12091600	`touch` `touch -t <DATE> <FILENAME>`
Create and remove directories `-rf` Forcefully remove a directory that contains files recursively	`mkdir <NEW_DIRECTORY>` `rmdir <DIRECTORY_TO_DELETE>`
Moving or Renaming a file Simply rename a file Move a file to another location, while possibly changing its name at the same time.	`mv`
Removing a file `-f` forcefully remove a file `-r` interactively remove a file (ask before removing)	`rm`
Viewing files (or combine files) that are not very long It does not provide any scroll-back. View backwards, starting at the last line with `tac` `-n` shows line numbers	`cat` `tac`
chmod builder	https://chmodcommand.com/
Restrict file so only owner can read `-R` to recursively change permissions for all folders and files below	`chmod 440 <FILE/FOLDER>` `chmod -R 400 <FILE/FOLDER>`
Make file executable	`chmod u+x <FILE>`
Count words in a file Default: lines, words, characters/bytes? `-l` Print the number of lines. `-w` Print the number of words. `-m` Print the number of characters. `-c` Print the number of bytes. `-L` Print the length of the longest line	`wc`
View larger files with a paging program It pauses at each screen full of text, provides scroll-back capabilities, and lets you search and navigate within the file. Use spacebar to paginate Use `/` to search for a pattern in the forward direction and `?` for a pattern in the backward direction. An older program named more is still used, but has fewer capabilities: "less is more". `-N` shows line numbers	`less`
Show the first few lines of a file Same modifiers as tails	`head`
Shows the last few lines of a file Print the last 10 lines of a file by default Change the number of lines by doing `-n 15` or just `-15` if you wanted to look at the last 15 lines instead of the default.	`tail` `tail 15` `tail -n 15`
Used to view documentation	`man`
Find where a program resides on the filesystem If a program isn't found with `which` then try `whereis` as it looks at a broader range of locations	`which <PROGRAM_NAME>`
Show home directory path for current user	`echo $HOME`
Change directory `cd ~` or just `cd` changes to Home directory `cd ..` changes to parent directory (..) `cd -` changes to previous directory (- (minus))	`cd` `cd ~` `cd ..` `cd -`
Move to a new directory but save the current directory for quick return `pushd` moves you to the directory specified in the argument `popd` returns you to the most recent directory from the last `pushd` command (so similar to `cd -` but saves it, even if you go to multiple `cd` commands between) `dirs` displays the current list of all directories saved with `pushd`	`pushd <NEW_DIRECTORY>` `popd` `dirs`
Find a file that contains specific text `-r` or `-R` is recursive `-n` is line number `-w` stands for match the whole word `-l` (lower-case L) can be added to just give the file name of matching files `-e` is the pattern used during the search	`grep -rnw '<PATH>/<TO>/<SOMEWHERE>' -e '<TEXT>'`
Count number of files in this directory and all sub-directories `.` look in current directory `-name` looks for files with the following name `-iname` ignores case of the name `-type` restrict the results to files of a certain specified type `d` for directory `l` for symbolic link `f` for a regular file `*` wildcard matches any string of characters `?` wildcard matches any single character `-ls` shows additional information about files found `-maxdepth` limits results to a max depth specified `-size` looks for files with specified size	`find` `find . -name "<FILE/DIRECTORY_NAME>"` `find . -name "test" -ls` `find . -type f -name "test" -ls` `find . -type d -maxdepth 1` `find . -size 0`
Search all files and directories on the sys Uses a local DB to index all files, so it can be faster than `find` but also out of date (updates once per day) DB can be manually updated using `sudo updatedb`	`locate`
Search for a specific package	`sudo dpkg --list \| grep <PACKAGE_NAME>`
Total disk space used (disk usage) by current directory and all sub-directories `-h` shows sizes in human readable format `-s` summarize at the current depth Shows size of all folders (and everything they contain) and files at the selected location `-a` the all flag lists the sizes of all files and directories in the given file path. This option is often combined with the `-h` flag for ease of use. Notice the individual file sizes are listed with the directories. `-c` Shows the total of all disk usage for the given file path as a new line at the bottom `*` use for current location Useful notes on arguments: https://www.redhat.com/sysadmin/du-command-options	`du -sh <LOCATION>` `du -sh <LOCATION>/` `du -sh ` `du -shc *`
Shows size of directories `-T` shows type of directory `-h` shows sizes in human readable format	`df -Th`
See if a service is running	`service <service-name> status` `service --status-all`
Search terminal history Keep pressing to search through previous commands that match	`ctrl-r`
Shows running processes and Env Args I think the ww does line wrapping	`ps -auxww`
Unrar unrars to the directory you are currently in	`sudo unrar x <FILENAME>.rar`
Run last command So to run the last command as sudo if you forget to add it to the start: sudo !!	`!!`
Open a file using sudo in a GUI application on Mac	`sudo open -a <APPLICATION_NAME> /file/to/open`
Show IP	`ifconfig`
Run command as a different user: sudo = be root so I can do anything. su means "now be another user” When you run su as root, you don't need to provide the users' password So "sudo su" means "run command as other user, and only have to enter root password" Command to run = -c	`sudo su postgres -c "psql"`
How to Kill Processes https://www.cyberciti.biz/faq/kill-process-in-linux-or-terminate-a-process-in-unix-or-linux-systems/ -15: the default way to kill a process -9: Last resort way to kill a process	`sudo kill -15 <PID>`
Terminal command history `-c` delete current session history	`history` `history -c`
Delete all terminal command history	`sudo rm ~/.bash_history`
Diff	`diff -arq /Diretory1 /Directory2`
Find a file by name	`sudo find / -type f -name “pg_hba.conf"`
Find a directory by name	`find / -type d -name "post*"`
Change user Leave empty to change to root user	`su`
On a clean install, grant current user sudo powers	`su` `<ENTER ROOT PASSWORD>` `echo "<USERNAME> ALL=(ALL) ALL" >` `/etc/sudoers.d/<USERNAME>` `chmod 440 /etc/sudoers.d/<USERNAME>`
Shutdown / restart Requires sudo `-h` apparently this isn't actually needed `-r` restarts instead of shutting down `now` shuts it down immediately otherwise it will default to a 60 second delay All arguments	`sudo shutdown -r now` `sudo shutdown -h 10:00 "Shutting down for scheduled maintenance."`
Use a shell command in-line	`ls -l $(dpkg --listfiles ftp)`
Open an image from the command line	`eog <IMAGE_FILE>`
Alias a command persistently directly from the command line and reload terminal This is faster than opening the ~/.bashrc file manually and adding the line directly `source ~/.bashrc` reloads the new parameters into the current terminal session	`echo "alias ls='ls -la'" >> ~/.bashrc` `source ~/.bashrc`
Check public facing ip	`curl https://ipinfo.io/ip`
Show interface configuration	`ifconfig`
Kernel IP routing table	`netstat -rn`
List all ip routing tables	`ip route show table all \| grep -Po 'table \K[^\s]+' \| sort -u`
Show content of ip routing table	`ip route list table <TABLE_NAME>`
Delete ip routing table	`sudo ip route flush table <TABLE_NAME>`
Disable and uninstall SSH	`sudo systemctl stop ssh` `sudo apt-get --purge remove ssh`
rsync large files and directories `-P` show progress `-a` archive (good for large files or unstable connections) Keeps a record of both sides of transfer to make sure it is successful even if it drops out temporarily in the middle `-v` verbose `-e` specify remote shell to use	`sudo rsync -Pav -e "ssh -i $HOME/Keys/<SSH_KEYS>.pem" <SOURCE_LOCATION> <DEST_USER>@<DEST_IP>:<DEST_LOCATION>` `sudo rsync -Pav -e "ssh -i $HOME/keys/Dev-Validator-Keys.pem" ~/TestDir ubuntu@172.31.31.109:~/`
Find all files changed in the last 5 minutes starting at the `/` root directory to a maxdepth of 10 not including the paths `/pro/` and `/sys/` Show updated time next to each file and folder	`sudo find / -maxdepth 10 -not -path "/proc/" -and -not -path "/sys/" -mmin -5 -printf "%p %TY-%Tm-%Td %TH:%TM \n"`
Change username `-l` flag to specify new name	`usermod -l <NEW_NAME> <OLD_NAME>`
Change groupname `-n` flag to specify new name	`groupmod -n <NEW_NAME> <OLD_NAME>`
UFW - Show all rules even when UFW is disabled	`sudo ufw show added`
Compress `tar.gz`	`tar -czvf archive.tar.gz stuff`
Extract `tar.gz`	`tar -xzvf archive.tar.gz`
Compress `tar.xz`	`tar -cJf archive.tar.xz stuff`
Extract `tar.xz`	`tar -xvf archive.tar.xz`
Show all available kernels	`dpkg --list \| grep linux-image`
Show current kernel	`uname -r`
Remove kernel version	`sudo apt remove -y linux-image-`