Tag: Linux Server

Linux Oct 23, 2016

Dirty COW and Other Linux Kernel Flaws: How to Check and Patch Your Kernel (2026)

Dirty COW is a 2016 Linux kernel flaw that let a local user gain root. Every supported Linux release has been patched for years, so if your server gets regular updates, you are safe from it. What matters today is the same habit for newer kernel flaws: update the kernel package, reboot or live-patch so the new kernel actually runs, and check the running version with uname -r.

Read article 6 min read

Hosting Guides Oct 1, 2016

How to Install Varnish Cache in Front of Apache (AlmaLinux, Rocky Linux and Ubuntu)

Install Varnish from your distribution's packages (dnf install varnish or apt install varnish), move Apache to port 8080, point Varnish's backend at 127.0.0.1:8080 in /etc/varnish/default.vcl, and make Varnish listen on port 80. Varnish does not handle HTTPS, so put Nginx or Hitch in front of it on port 443. Test with curl -I and look for the X-Varnish and Age headers. On cPanel servers, use NGINX Manager in WHM instead.

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Control Panels Mar 7, 2016

Free SSL in 2026: Let’s Encrypt on cPanel (AutoSSL) and on Linux Servers (Certbot)

On a cPanel server, use AutoSSL: in WHM open SSL/TLS > Manage AutoSSL, choose a provider, and run it for all users. Certificates install and renew on their own. On a server without a control panel, install Certbot and run sudo certbot --nginx or sudo certbot --apache. Certbot sets up automatic renewal. Check renewal with sudo certbot renew --dry-run.

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cPanel & WHM Feb 27, 2016

How to Install and Use Linux Malware Detect (LMD, maldet) on Linux and cPanel (2026)

Linux Malware Detect (LMD) is an open-source malware scanner for Linux systems, specifically designed for shared hosting environments. It leverages real-time threat intelligence from network intrusion detection systems and community submissions to identify and eliminate malware. LMD integrates seamlessly with ClamAV to enhance scanning capabilities using both MD5 hash-based and HEX pattern matching detection techniques.

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Linux Feb 27, 2016

How to Install and Use Rkhunter (Rootkit Hunter) on Linux Servers (2026)

Install rkhunter from your distribution's packages (dnf install rkhunter from EPEL on AlmaLinux, Rocky Linux and CloudLinux, or apt install rkhunter on Debian and Ubuntu). Then update its data files with rkhunter --update, record a baseline of your system files with rkhunter --propupd, and scan with rkhunter --check --sk. Set an email address for warnings and let the daily cron job run. Run --propupd again after every system update, or you will get false warnings.

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Linux Feb 25, 2016

How to Check and Repair a Linux Filesystem (fsck for ext4, xfs_repair for XFS)

Find the device and its filesystem type with lsblk -f. For ext4, unmount it and run fsck -n /dev/DEVICE to check, then fsck -y /dev/DEVICE to repair. For XFS, the default on AlmaLinux and Rocky Linux, use xfs_repair -n and xfs_repair instead, because fsck does nothing on XFS. The root filesystem cannot be unmounted, so repair it from rescue mode or force a check at the next boot.

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Hosting Guides Feb 25, 2016

How to Install and Use htop on Linux: Read the Screen, Find Busy Processes

Learn how to install and use htop on all major Linux distributions. A powerful alternative to top, with real-time monitoring, mouse support, and modern features.

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Linux Feb 25, 2016

Common SSH Commands or Linux Shell Commands

Master critical SSH and Linux shell commands with UnderHost.com. Discover how efficient server management starts with powerful terminal skills. Learn the commands that keep your offshore servers, cloud hosting, and dedicated servers running smoothly.

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Control Panels Feb 25, 2016

How to Install and Configure CSF Firewall (v15 GPL) on cPanel and Linux Servers

ConfigServer Security & Firewall (CSF) is a popular firewall for Linux servers that includes a login failure daemon (lfd) to detect and block brute-force attacks. This guide will walk you through installing and configuring CSF on your server.

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UnderHost Blog

Guides, security notes and news for modern hosting.

Practical, real-world articles on offshore hosting, Linux and cPanel administration, server security and the technology behind our network, written by the UnderHost team.