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+---
+title: List of essential Linux commands for server management
+permalink: /linux-cheatsheet.html
+date: 2021-08-01T12:00:00+02:00
+layout: post
+type: post
+draft: false
+---
+
+**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
+```
+