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+---
+title: List of essential Linux commands for server management
+url: linux-cheatsheet.html
+date: 2021-08-01
+draft: false
+---
+
+**Table of contents**
+
+1. [Generate SSH key](#generate-ssh-key)
+2. [Login to host via SSH](#login-to-host-via-ssh)
+3. [Execute command on a server through SSH](#execute-command-on-a-server-through-ssh)
+4. [Displays currently logged in users in the system](#displays-currently-logged-in-users-in-the-system)
+5. [Displays Linux system information](#displays-linux-system-information)
+6. [Displays kernel release information](#displays-kernel-release-information)
+7. [Shows the system hostname](#shows-the-system-hostname)
+8. [Shows system reboot history](#shows-system-reboot-history)
+9. [Displays information about the user](#displays-information-about-the-user)
+10. [Displays IP addresses and all the network interfaces](#displays-ip-addresses-and-all-the-network-interfaces)
+11. [Downloads a file from an online source](#downloads-a-file-from-an-online-source)
+12. [Compress a file with gzip](#compress-a-file-with-gzip)
+13. [Interactive disk usage analyzer](#interactive-disk-usage-analyzer)
+14. [Install Node.js using the Node Version Manager](#install-nodejs-using-the-node-version-manager)
+15. [Too long; didn't read](#too-long-didnt-read)
+16. [Combine all Nginx access logs to one big log file](#combine-all-nginx-access-logs-to-one-big-log-file)
+17. [Set up Redis server](#set-up-redis-server)
+18. [Generate statistics of your webserver](#generate-statistics-of-your-webserver)
+19. [Search for a given pattern in files](#search-for-a-given-pattern-in-files)
+20. [Find proccess ID for a specific program](#find-proccess-id-for-a-specific-program)
+21. [Print name of current/working directory](#print-name-of-currentworking-directory)
+22. [Creates a blank new file](#creates-a-blank-new-file)
+23. [Displays first lines in a file](#displays-first-lines-in-a-file)
+24. [Displays last lines in a file](#displays-last-lines-in-a-file)
+25. [Count lines in a file](#count-lines-in-a-file)
+26. [Find all instances of the file](#find-all-instances-of-the-file)
+27. [Find file names that begin with ‘index’ in /home folder](#find-file-names-that-begin-with-index-in-home-folder)
+28. [Find files larger than 100MB in the home folder](#find-files-larger-than-100mb-in-the-home-folder)
+29. [Displays block devices related information](#displays-block-devices-related-information)
+30. [Displays free space on mounted systems](#displays-free-space-on-mounted-systems)
+31. [Displays free and used memory in the system](#displays-free-and-used-memory-in-the-system)
+32. [Displays all active listening ports](#displays-all-active-listening-ports)
+33. [Kill a process violently](#kill-a-process-violently)
+34. [List files opened by user](#list-files-opened-by-user)
+35. [Execute "df -h", showing periodic updates](#execute-df--h-showing-periodic-updates)
+
+
+##### Generate SSH key
+
+```bash
+ssh-keygen -t ed25519 -C "your_email@example.com"
+
+# when no support for Ed25519 present
+ssh-keygen -t rsa -b 4096 -C "your_email@example.com"
+```
+
+Note: By default SSH keys get stored to `/home/<username>/.ssh/` folder.
+
+
+
+##### Login to host via SSH
+
+```bash
+# connect to host as your local username
+ssh host
+
+# connect to host as user
+ssh <user>@<host>
+
+# connect to host using port
+ssh -p <port> <user>@<host>
+```
+
+
+
+##### Execute command on a server through SSH
+
+```bash
+# execute one command
+ssh root@100.100.100.100 "ls /root"
+
+# execute many commands
+ssh root@100.100.100.100 "cd /root;touch file.txt"
+```
+
+
+
+##### Displays currently logged in users in the system
+
+```bash
+w
+```
+
+
+
+##### Displays Linux system information
+
+```bash
+uname
+```
+
+
+
+##### Displays kernel release information
+
+```bash
+uname -r
+```
+
+
+
+##### Shows the system hostname
+
+```bash
+hostname
+```
+
+
+
+##### Shows system reboot history
+
+```bash
+last reboot
+```
+
+
+
+##### Displays information about the user
+
+```bash
+sudo apt install finger
+finger <username>
+```
+
+
+
+##### Displays IP addresses and all the network interfaces
+
+```bash
+ip addr show
+```
+
+
+
+##### Downloads a file from an online source
+
+```bash
+wget https://example.com/example.tgz
+```
+
+Note: If URL contains ?, & enclose the URL in double quotes.
+
+
+
+##### Compress a file with gzip
+
+```bash
+# will not keep the original file
+gzip file.txt
+
+# will keep the original file
+gzip --keep file.txt
+```
+
+
+
+##### Interactive disk usage analyzer
+
+```bash
+sudo apt install ncdu
+
+ncdu
+ncdu <path/to/directory>
+```
+
+
+
+##### Install Node.js using the Node Version Manager
+
+```bash
+curl -o- https://raw.githubusercontent.com/nvm-sh/nvm/v0.35.3/install.sh | bash
+source ~/.bashrc
+
+nvm install v13
+```
+
+
+
+##### Too long; didn't read
+
+```bash
+npm install -g tldr
+
+tldr tar
+```
+
+
+
+##### Combine all Nginx access logs to one big log file
+
+```bash
+zcat -f /var/log/nginx/access.log* > /var/log/nginx/access-all.log
+```
+
+
+
+##### Set up Redis server
+
+```bash
+sudo apt install redis-server redis-tools
+
+# check if server is running
+sudo service redis status
+
+# set and get a key value
+redis-cli set mykey myvalue
+redis-cli get mykey
+
+# interactive shell
+redis-cli
+```
+
+
+
+##### Generate statistics of your webserver
+
+```bash
+sudo apt install goaccess
+
+# check if installed
+goaccess -v
+
+# combine logs
+zcat -f /var/log/nginx/access.log* > /var/log/nginx/access-all.log
+
+# export to single html
+goaccess \
+  --log-file=/var/log/nginx/access-all.log \
+  --log-format=COMBINED \
+  --exclude-ip=0.0.0.0 \
+  --ignore-crawlers \
+  --real-os \
+  --output=/var/www/html/stats.html
+
+# cleanup afterwards
+rm /var/log/nginx/access-all.log
+```
+
+
+
+##### Search for a given pattern in files
+
+```bash
+grep -r ‘pattern’ files
+```
+
+
+
+##### Find proccess ID for a specific program
+
+```bash
+pgrep nginx
+```
+
+
+
+##### Print name of current/working directory
+
+```bash
+pwd
+```
+
+
+
+##### Creates a blank new file
+
+```bash
+touch newfile.txt
+```
+
+
+
+##### Displays first lines in a file
+
+```bash
+# -n <x> presents the number of lines (10 by default)
+head -n 20 somefile.txt
+```
+
+
+
+##### Displays last lines in a file
+
+```bash
+# -n <x> presents the number of lines (10 by default)
+tail -n 20 somefile.txt
+
+# -f follows the changes in file (doesn't closes)
+tail -f somefile.txt
+```
+
+
+
+##### Count lines in a file
+
+```bash
+wc -l somefile.txt
+```
+
+
+
+##### Find all instances of the file
+
+```bash
+sudo apt install mlocate
+
+locate somefile.txt
+```
+
+
+
+##### Find file names that begin with ‘index’ in /home folder
+
+```bash
+find /home/ -name "index"
+```
+
+
+
+##### Find files larger than 100MB in the home folder
+
+```bash
+find /home -size +100M
+```
+
+
+
+##### Displays block devices related information
+
+```bash
+lsblk
+```
+
+
+
+##### Displays free space on mounted systems
+
+```bash
+df -h
+```
+
+
+
+##### Displays free and used memory in the system
+
+```bash
+free -h
+```
+
+
+
+##### Displays all active listening ports
+
+```bash
+sudo apt install net-tools
+
+netstat -pnltu
+```
+
+
+
+##### Kill a process violently
+
+```bash
+kill -9 <pid>
+```
+
+
+
+##### List files opened by user
+
+```bash
+lsof -u <user>
+```
+
+
+
+##### Execute "df -h", showing periodic updates
+
+```bash
+# -n 1 means every second
+watch -n 1 df -h
+```
+
+
+