When you’re managing a Linux server remotely over SSH, determining whether a USB drive has been connected requires checking kernel messages and device listings since you can’t visually inspect the hardware. Check dmesg for USB Detection Events The most reliable method is examining kernel logs with dmesg. When a USB device is detected, the kernel…
GNU Screen is a terminal multiplexer that lets you manage multiple shell sessions within a single window. If you’re new to it, here are the best resources to get up to speed, plus practical tips for getting started. Getting Started with Screen For an introduction to the basics, start with A quick tutorial on screen….
Connecting your application to a MySQL database is fundamental to most backend systems. Rather than shelling out to the mysql command-line client, you’ll use language-specific connectors that provide proper connection pooling, error handling, and prepared statements. Language-Specific MySQL Drivers The best approach depends on your tech stack: Python Use mysql-connector-python for straightforward connections or PyMySQL…
Managing a cluster of servers, you’ll want to be notified when they come back online after restarts or unexpected reboots. Email notifications on boot let you track infrastructure changes and catch potential issues early. Using crontab @reboot The simplest approach is a crontab @reboot entry that runs once at startup. This executes before most services…
When a filesystem listed in /etc/fstab fails to mount during boot, the system can hang or drop to an emergency shell, preventing normal startup. This happens because the kernel treats all mount entries equally by default. Non-critical filesystems—network shares, external drives, or optional data partitions—shouldn’t block your entire system from booting. Understanding fstab mount options…
When a kernel panic occurs on a remote Linux server, manual intervention via SSH becomes impossible. The kernel can be configured to automatically reboot after a panic, allowing the system to recover without human intervention. Enable Kernel Panic Auto-Reboot The kernel.panic parameter controls this behavior. A value of 0 disables auto-reboot; any positive integer specifies…
Rocky Linux 9 can blank the console screen after a period of inactivity, but by default it may not actually power off the display. This is often caused by kernel mode settings or DPMS (Display Power Management Signaling) configuration. Check Current DPMS Status First, verify whether DPMS is enabled on your console: cat /sys/module/kernel/parameters/consoleblank If…
MPlayer has been largely superseded by mpv in most Linux distributions, but if you need the classic MPlayer with DVD navigation support, building from source remains the way to get libdvdnav integrated. Most distribution packages omit this feature due to licensing complexity. Prerequisites You’ll need a C compiler, build tools, and development libraries. On Fedora/RHEL-based…
Rate-limiting SSH brute-force attempts is essential for any server exposed to the internet. Using iptables with the recent module, you can drop connections from IPs that exceed a threshold in a given time window—for example, blocking IPs that attempt more than 6 connections in 60 seconds. Using iptables The recent module tracks connection attempts by…
When managing packages on Ubuntu or Debian systems, knowing what versions are available—and which one will be installed—is essential for dependency management and system stability. The aptitude command provides several ways to inspect package versions. Check all available versions of a package The most straightforward approach is to use the versions subcommand: aptitude versions package-name…
Xterm doesn’t send Alt key escape sequences by default, which breaks Alt-based keybindings in Vim, Emacs, shell readline, and other applications. Here’s how to fix it across different terminal setups. Xterm Configuration Add this to your ~/.Xresources file: xterm*metaSendsEscape: true Then load the changes and restart xterm: xrdb -merge ~/.Xresources xterm & This tells xterm…
When you create a new branch locally and try to git pull, you’ll hit this error if the branch doesn’t have upstream tracking configured: You asked me to pull without telling me which branch you want to merge with, and ‘branch.dev-harry.merge’ in your configuration file does not tell me, either. This happens because Git doesn’t…
When you run cat /etc/resolv.conf on a modern Linux system, you’ll often see nameserver 127.0.0.1 or 127.0.1.1 pointing to localhost. This doesn’t mean you’re actually using your ISP’s DNS directly — it usually means your system is running a local DNS stub resolver or caching service like systemd-resolved or dnsmasq. To find out which actual…
When you need to change the commit message of a past commit that isn’t HEAD, git commit –amend alone won’t help. You’ll need to use interactive rebase to stop at that commit, amend it, and then continue. Interactive Rebase to Edit a Commit The core approach is git rebase -i with the commit hash. Say…
If you’re running Google AdSense on your site, you might want to show ads only to desktop visitors and hide them on mobile devices. This reduces clutter on smaller screens and can sometimes improve user experience—though test your bounce rates to confirm it actually helps your metrics. Using CSS Media Queries The cleanest approach is…
Attaching storage to a running Xen DomU without rebooting is straightforward using the xl toolstack. This is useful when you need to add capacity, attach backup storage, or provision new volumes without downtime. Basic Disk Attachment To attach a logical volume or physical disk to a running DomU, use xl block-attach on Dom0: xl block-attach…
When working with non-standard C file extensions, Vim’s taglist plugin and filetype detection won’t automatically recognize them. You need to explicitly tell Vim to treat those files as C source. Basic approach Add this to your ~/.vimrc: autocmd BufRead,BufNewFile *.c0 set filetype=c Replace *.c0 with whatever extension you’re using. This tells Vim that any file…
When you need to share work in progress or maintain a separate feature branch on a remote Git server, you’ll need to create a local branch and push it upstream. Here’s how to do it properly. Basic workflow The fundamental process involves three steps: Create a local branch and switch to it Make changes and…
When managing a Linux system remotely, you sometimes need to terminate all sessions for a specific user—whether they’re logged in locally at the console, via SSH, through X11 forwarding, VNC, or any other method. Here’s how to do it. Quick Answer To terminate all processes for a user named bob: killall -u bob This kills…
When you SSH to a server and see the warning below, your SSH client has detected that the server’s host key doesn’t match what’s stored locally: @@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@ @ WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED! @ @@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@ IT IS POSSIBLE THAT SOMEONE IS DOING SOMETHING NASTY! Someone could be eavesdropping on you right now (man-in-the-middle attack)!…