day14.md

On the forteenth day, I learned the following things about Linux.

• In Linux, an alias is a shortcut that references a command. Aliases are mostly used to replace long commands, improving efficiency and avoiding potential spelling errors.

• alias will show you all the aliases that are generated.

• alias <key>="<value>" will make a new alias and after that, if you type a key, a functionality according to a value will be performed.

• unalias <key> will remove an alias from the memory and after that, the key will not be functional.

Q. What if you want to create multiple aliases at once?

A. You can store them in a file.

• nano ~/.zshrc will open up a zsh file in which you can store the aliases.

• alias <key>="<value>" is the format of giving an alias to a file.

• source ~/.zshrc will activate the alias that you saved in a file. Without activation you can't execute the alias.

Note: The same pattern will be applied to the bash terminal also. You just need to write ~/.bashrc instead of ~/.zshrc.

• Ctrl+A will move you to the first point of the command.

• Ctrl+E will move you to the end point of the command.

• Ctrl+U will delete everything that you entered.

• Ctrl+K will delete the command from the back of the cursor.

• Ctrl+R will search for the previous command.

• TAB button will auto complete the command without writing it as a whole.

• !<number> will take a number from the history and run it to access that command.

• !<command> will take a command from the history that was used last time and run it to access that command.

• ; will help you to add multiple commands in one line.

• sort file-name will sort the data in an alphabetical order.

• sort -r file-name is the reverse of the sort.

• sort -n file-name will return the data in a numerical order.

• jobs will display all the current processes that are running.

• ping website will display all the data packets from a particular server.

• wget <URL> will download files from the internet.

• wget -O file-name <URL> will save the downloaded file under a different name.

• top will show that how many processes are running and how much CPU usage is consuming?

• kill process ID will close the process.

• uname will display the kernel name.

• uname -o will print the operating system.

• uname -m will print the architecture.

• uname -v will print the kernel version.

• cat /etc/os-release will give the information of your operating system.

• lscpu will give you the CPU details.

• free will show you the free memory.

• vmstat will display the virtual memory state.

• id will print the IDs, group ids and stuff.

• getent group username will look up the user details on Linux.

• zip zip-file.zip text-file.txt will zip the text-file.txt into zip-file.txt.

• unzip zip-file.zip will unzip the file.

• hostname will show the hostname.

• hostname -i will show the ip-address.

• useradd username will add a new user.

• passwd username will give a password to the user.

• userdel username will delete a username.

• lsof will list all the open files.

• lsof -u username will list the files that are opened by a username.

• nslookup website will give the ip-address of a website.

• netstat will give the details of all the active ports.

• ps aux will give a snapshot of the current processes.

• cut -c 1-2 file-name will remove sections from each line of files.

• ping website1 & ping website2 "&" operator will fetch multiple sites data.

• echo "first" && echo "second" "&&" operator will say if the first command is executed then execute the second command.

• echo "hey" && {echo "hi"; echo "I am good"} will say that if the first echo is executed then execute the commands in curly braces.

• echo "first" || echo "second" "||" operator will say if the first command is not executed then execute the second one.

• | (pipe) will send the output from the first command to the second command.

Explaining it in a video

Here you can get an explanation in a video. 14/60 Day of DevOps Challenge