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<a href=/index.xml target=_blank>RSS</a></nav></header><main role=main><article itemtype=http://schema.org/Article><h1 itemtype=headline>List of essential Linux commands for server management</h1><p><cap>post</cap>, Aug 1, 2021 on <a href=https://mitjafelicijan.com>Mitja Felicijan's blog</a><div><p><strong>Generate SSH key</strong><pre tabindex=0 style=background-color:#fff><code><span style=display:flex><span>ssh-keygen -t ed25519 -C <span style=color:#a31515>&#34;your_email@example.com&#34;</span>
</span></span><span style=display:flex><span>
</span></span><span style=display:flex><span><span style=color:green># when no support for Ed25519 present</span>
</span></span><span style=display:flex><span>ssh-keygen -t rsa -b 4096 -C <span style=color:#a31515>&#34;your_email@example.com&#34;</span>
</span></span></code></pre><p>Note: By default SSH keys get stored to <code>/home/&lt;username>/.ssh/</code> folder.<p><strong>Login to host via SSH</strong><pre tabindex=0 style=background-color:#fff><code><span style=display:flex><span><span style=color:green># connect to host as your local username</span>
</span></span><span style=display:flex><span>ssh host
</span></span><span style=display:flex><span>
</span></span><span style=display:flex><span><span style=color:green># connect to host as user</span>
</span></span><span style=display:flex><span>ssh &lt;user&gt;@&lt;host&gt;
</span></span><span style=display:flex><span>
</span></span><span style=display:flex><span><span style=color:green># connect to host using port</span>
</span></span><span style=display:flex><span>ssh -p &lt;port&gt; &lt;user&gt;@&lt;host&gt;
</span></span></code></pre><p><strong>Execute command on a server through SSH</strong><pre tabindex=0 style=background-color:#fff><code><span style=display:flex><span><span style=color:green># execute one command</span>
</span></span><span style=display:flex><span>ssh root@100.100.100.100 <span style=color:#a31515>&#34;ls /root&#34;</span>
</span></span><span style=display:flex><span>
</span></span><span style=display:flex><span><span style=color:green># execute many commands</span>
</span></span><span style=display:flex><span>ssh root@100.100.100.100 <span style=color:#a31515>&#34;cd /root;touch file.txt&#34;</span>
</span></span></code></pre><p><strong>Displays currently logged in users in the system</strong><pre tabindex=0 style=background-color:#fff><code><span style=display:flex><span>w
</span></span></code></pre><p><strong>Displays Linux system information</strong><pre tabindex=0 style=background-color:#fff><code><span style=display:flex><span>uname
</span></span></code></pre><p><strong>Displays kernel release information</strong><pre tabindex=0 style=background-color:#fff><code><span style=display:flex><span>uname -r
</span></span></code></pre><p><strong>Shows the system hostname</strong><pre tabindex=0 style=background-color:#fff><code><span style=display:flex><span>hostname
</span></span></code></pre><p><strong>Shows system reboot history</strong><pre tabindex=0 style=background-color:#fff><code><span style=display:flex><span>last reboot
</span></span></code></pre><p><strong>Displays information about the user</strong><pre tabindex=0 style=background-color:#fff><code><span style=display:flex><span>sudo apt install finger
</span></span><span style=display:flex><span>finger &lt;username&gt;
</span></span></code></pre><p><strong>Displays IP addresses and all the network interfaces</strong><pre tabindex=0 style=background-color:#fff><code><span style=display:flex><span>ip addr show
</span></span></code></pre><p><strong>Downloads a file from an online source</strong><pre tabindex=0 style=background-color:#fff><code><span style=display:flex><span>wget https://example.com/example.tgz
</span></span></code></pre><p>Note: If URL contains ?, & enclose the URL in double quotes.<p><strong>Compress a file with gzip</strong><pre tabindex=0 style=background-color:#fff><code><span style=display:flex><span><span style=color:green># will not keep the original file</span>
</span></span><span style=display:flex><span>gzip file.txt
</span></span><span style=display:flex><span>
</span></span><span style=display:flex><span><span style=color:green># will keep the original file</span>
</span></span><span style=display:flex><span>gzip --keep file.txt
</span></span></code></pre><p><strong>Interactive disk usage analyzer</strong><pre tabindex=0 style=background-color:#fff><code><span style=display:flex><span>sudo apt install ncdu
</span></span><span style=display:flex><span>
</span></span><span style=display:flex><span>ncdu
</span></span><span style=display:flex><span>ncdu &lt;path/to/directory&gt;
</span></span></code></pre><p><strong>Install Node.js using the Node Version Manager</strong><pre tabindex=0 style=background-color:#fff><code><span style=display:flex><span>curl -o- https://raw.githubusercontent.com/nvm-sh/nvm/v0.35.3/install.sh | bash
</span></span><span style=display:flex><span>source ~/.bashrc
</span></span><span style=display:flex><span>
</span></span><span style=display:flex><span>nvm install v13
</span></span></code></pre><p><strong>Too long; didn't read</strong><pre tabindex=0 style=background-color:#fff><code><span style=display:flex><span>npm install -g tldr
</span></span><span style=display:flex><span>
</span></span><span style=display:flex><span>tldr tar
</span></span></code></pre><p><strong>Combine all Nginx access logs to one big log file</strong><pre tabindex=0 style=background-color:#fff><code><span style=display:flex><span>zcat -f /var/log/nginx/access.log* &gt; /var/log/nginx/access-all.log
</span></span></code></pre><p><strong>Set up Redis server</strong><pre tabindex=0 style=background-color:#fff><code><span style=display:flex><span>sudo apt install redis-server redis-tools
</span></span><span style=display:flex><span>
</span></span><span style=display:flex><span><span style=color:green># check if server is running</span>
</span></span><span style=display:flex><span>sudo service redis status
</span></span><span style=display:flex><span>
</span></span><span style=display:flex><span><span style=color:green># set and get a key value</span>
</span></span><span style=display:flex><span>redis-cli set mykey myvalue
</span></span><span style=display:flex><span>redis-cli get mykey
</span></span><span style=display:flex><span>
</span></span><span style=display:flex><span><span style=color:green># interactive shell</span>
</span></span><span style=display:flex><span>redis-cli
</span></span></code></pre><p><strong>Generate statistics of your webserver</strong><pre tabindex=0 style=background-color:#fff><code><span style=display:flex><span>sudo apt install goaccess
</span></span><span style=display:flex><span>
</span></span><span style=display:flex><span><span style=color:green># check if installed</span>
</span></span><span style=display:flex><span>goaccess -v
</span></span><span style=display:flex><span>
</span></span><span style=display:flex><span><span style=color:green># combine logs</span>
</span></span><span style=display:flex><span>zcat -f /var/log/nginx/access.log* &gt; /var/log/nginx/access-all.log
</span></span><span style=display:flex><span>
</span></span><span style=display:flex><span><span style=color:green># export to single html</span>
</span></span><span style=display:flex><span>goaccess <span style=color:#a31515>\
</span></span></span><span style=display:flex><span><span style=color:#a31515></span>  --log-file=/var/log/nginx/access-all.log <span style=color:#a31515>\
</span></span></span><span style=display:flex><span><span style=color:#a31515></span>  --log-format=COMBINED <span style=color:#a31515>\
</span></span></span><span style=display:flex><span><span style=color:#a31515></span>  --exclude-ip=0.0.0.0 <span style=color:#a31515>\
</span></span></span><span style=display:flex><span><span style=color:#a31515></span>  --ignore-crawlers <span style=color:#a31515>\
</span></span></span><span style=display:flex><span><span style=color:#a31515></span>  --real-os <span style=color:#a31515>\
</span></span></span><span style=display:flex><span><span style=color:#a31515></span>  --output=/var/www/html/stats.html
</span></span><span style=display:flex><span>
</span></span><span style=display:flex><span><span style=color:green># cleanup afterwards</span>
</span></span><span style=display:flex><span>rm /var/log/nginx/access-all.log
</span></span></code></pre><p><strong>Search for a given pattern in files</strong><pre tabindex=0 style=background-color:#fff><code><span style=display:flex><span>grep -r ‘pattern’ files
</span></span></code></pre><p><strong>Find proccess ID for a specific program</strong><pre tabindex=0 style=background-color:#fff><code><span style=display:flex><span>pgrep nginx
</span></span></code></pre><p><strong>Print name of current/working directory</strong><pre tabindex=0 style=background-color:#fff><code><span style=display:flex><span>pwd
</span></span></code></pre><p><strong>Creates a blank new file</strong><pre tabindex=0 style=background-color:#fff><code><span style=display:flex><span>touch newfile.txt
</span></span></code></pre><p><strong>Displays first lines in a file</strong><pre tabindex=0 style=background-color:#fff><code><span style=display:flex><span><span style=color:green># -n &lt;x&gt; presents the number of lines (10 by default)</span>
</span></span><span style=display:flex><span>head -n 20 somefile.txt
</span></span></code></pre><p><strong>Displays last lines in a file</strong><pre tabindex=0 style=background-color:#fff><code><span style=display:flex><span><span style=color:green># -n &lt;x&gt; presents the number of lines (10 by default)</span>
</span></span><span style=display:flex><span>tail -n 20 somefile.txt
</span></span><span style=display:flex><span>
</span></span><span style=display:flex><span><span style=color:green># -f follows the changes in file (doesn&#39;t closes)</span>
</span></span><span style=display:flex><span>tail -f somefile.txt
</span></span></code></pre><p><strong>Count lines in a file</strong><pre tabindex=0 style=background-color:#fff><code><span style=display:flex><span>wc -l somefile.txt
</span></span></code></pre><p><strong>Find all instances of the file</strong><pre tabindex=0 style=background-color:#fff><code><span style=display:flex><span>sudo apt install mlocate
</span></span><span style=display:flex><span>
</span></span><span style=display:flex><span>locate somefile.txt
</span></span></code></pre><p><strong>Find file names that begin with ‘index’ in /home folder</strong><pre tabindex=0 style=background-color:#fff><code><span style=display:flex><span>find /home/ -name <span style=color:#a31515>&#34;index&#34;</span>
</span></span></code></pre><p><strong>Find files larger than 100MB in the home folder</strong><pre tabindex=0 style=background-color:#fff><code><span style=display:flex><span>find /home -size +100M
</span></span></code></pre><p><strong>Displays block devices related information</strong><pre tabindex=0 style=background-color:#fff><code><span style=display:flex><span>lsblk
</span></span></code></pre><p><strong>Displays free space on mounted systems</strong><pre tabindex=0 style=background-color:#fff><code><span style=display:flex><span>df -h
</span></span></code></pre><p><strong>Displays free and used memory in the system</strong><pre tabindex=0 style=background-color:#fff><code><span style=display:flex><span>free -h
</span></span></code></pre><p><strong>Displays all active listening ports</strong><pre tabindex=0 style=background-color:#fff><code><span style=display:flex><span>sudo apt install net-tools
</span></span><span style=display:flex><span>
</span></span><span style=display:flex><span>netstat -pnltu
</span></span></code></pre><p><strong>Kill a process violently</strong><pre tabindex=0 style=background-color:#fff><code><span style=display:flex><span>kill -9 &lt;pid&gt;
</span></span></code></pre><p><strong>List files opened by user</strong><pre tabindex=0 style=background-color:#fff><code><span style=display:flex><span>lsof -u &lt;user&gt;
</span></span></code></pre><p><strong>Execute "df -h", showing periodic updates</strong><pre tabindex=0 style=background-color:#fff><code><span style=display:flex><span><span style=color:green># -n 1 means every second</span>
</span></span><span style=display:flex><span>watch -n 1 df -h
</span></span></code></pre></div></article></main><section><hr><h2>Posts from blogs I follow around the net</h2><ul><li><a href=https://chotrin.org/writing/2023-10-29.html target=_blank rel=noopener>even more bike things.</a><div>I wrote about all sorts of biking and not-biking things in my life this week. — <a href=https://chotrin.org>chötrin's wiki.</a><li><a href="http://offbeatpursuit.com:80/blog/?id=25" target=_blank rel=noopener>A fix by any other name</a><div>tags:
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