From 52bfdaea11ec4ff5a8bc9b97fb86a2777b8b4511 Mon Sep 17 00:00:00 2001
From: Mitja Felicijan <mitja.felicijan@gmail.com>
Date: Sun, 1 Aug 2021 20:25:28 +0200
Subject: new post

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+---
+Title: List of essential Linux commands for server management
+Description: List of essential Linux commands for server management
+Slug: linux-cheatsheet
+Listing: true
+Created: 2021-08-01
+Tags: []
+---
+
+***For Debian and Ubuntu servers***
+
+
+
+
+
+##### 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 +10000M
+```
+
+
+
+##### 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
+```
+
+
+
-- 
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