66 lines
5.0 KiB
Markdown
66 lines
5.0 KiB
Markdown
---
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title: Simple and Useful Linux Commands for Daily use and Operations
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---
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# Simple and Useful Linux Commands
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The commands listed here are basic, and will help you get started quickly. But they’re also powerful, and they’ll continue to be useful as your Linux expertise expands.
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1. `echo` This takes the text you give it and sends it somewhere—back to the screen, to a file, or to another command. By default it echoes back to the screen, unless used with redirection `>`
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Example: `echo "hello!"`
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Example 2: `echo "Hello world" > hello.txt`
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2. `cat` To display the contents of a text file, just type `cat myfile`. This command can display multiple files one after another by concatenating them into one string, hence the name. Just type `cat myfile1 myfile2`.
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3. `find` It does what it says, and it’s good at it. Use it to locate files by path, size, date, owner and a bunch of other useful filters. Example: `find . -type f -mtime -1h # List files in this directory modified in the past hour`.
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4. `date` Just type date when you want to know what time it is. Example: `date "+It's %l:%m%p on %A"`. Use it in a script to name files according to the current date.
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5. `ls` What's in this directory? Combine `ls` with some useful flags to display and sort directory contents by date and size. It also gives you lots of options for formatting the output.
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6. `pwd` Where am I? Linux can be unforgiving, particularly when you delete something. Make sure you know are before you issue your commands.
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7. `mail` Linux's mail program isn’t good looking, but it can be really helpful. You can create a message and add text, recipients, and attachments all in one command. Example: `echo "We're having a great time." | mail -s "Wish you were here!" -A postcard.png -t mom@example.com`
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8. `cut` When you have a string with separators in it, use `cut` to filter out certain fields. Example: `echo "this, that, and the other" | cut -d, -f2 # "that"`
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9. `grep` To find lines of text that contain a certain string, use grep. Example: `grep 'root' /etc/passwd # root:x:0:0:root:/root:/bin/bash`
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10. `sed` Use sed to find and change a substring in a piece of text. Example: `echo "this, that, and the other" | sed 's/that/those/' # "this, those, and the other"`
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11. `shutdown` use shut down the system and turn off the power. Example: `shutdown -h now`shuts down system immediately. `shutdown -h +5` shuts down system after five minutes. You can also reboot the system immediately by issuing the command `shutdown -r now`.
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12. `cd` use `cd` to change the directory. Example: `cd dirName` changes the directory to the folder names `dirName`. `cd ..` this command takes to the upper root folder or out of the folder.
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Use these commands in scripts and at the command line. They're all very powerful commands, and Linux's man page has a lot more information about each one.
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***********
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Also, important commands used for System Administrators are following:
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1. `uptime`
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It shows since how long your system is running and the number of users who are currently logged in. It also displays the load averages for 1, 5 and 15 minutes intervals.
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2. `w`
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It displays currently logged in users and their processes along-with load averages. It also shows the login name, tty name, remote host, login time, idle time, JCPU, PCPU, command and processes.
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3. `users`
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It displays currently logged in users. This command doesn’t have parameters other than 'help' and 'version'.
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4. `who`
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It simply returns user name, date, time and host information. `who` command is similar to `w` command. Unlike `w` command, `who` doesn’t print what users are doing.
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5. `whoami`
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It prints the name of current user. You can also use “who am i” command to display the current user. If you are logged in as a root using sudo command “whoami” command return root as current user. Use “who am i” command if you want to know the exact user logged in.
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6. `ls`
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It displays the list of files in human readable format.
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7. `crontab`
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List schedule jobs for current user with crontab command and -l option.
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8. `less`
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It allows quickly view file. You can page up and down. Press `q` to quit from `less` window.
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9. `more`
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It allows quickly view file and shows details in percentage. You can page up and down. Press `q` to quit from `more` window.
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10. `cp`
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Copy file from source to destination preserving same mode.
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11. `mv`
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Move file from source to destination preserving same mode.
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12. `ifconfig` to view ip and other information.
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13. `systemctl` Command
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This is a command which allows operators to work with the Linux system services. The standard use of the command is `systemctl <OPTION> <SERVICE-NAME>` by providing an `OPTION` (e.g. `start`, `stop`, `status`) and than providing a specific Service Name to act on. You can use the command to get a general status of your Linux services (e.g `systemctl status`). Note that you will either need Administrator access or use `sudo` to elevate your rights to run the command successfully.
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These commands are frequently used by adminstrators. This is not a complete list, but it’s a compact list to refer to when needed.
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