When you need to traverse a directory tree in Python, you have several options. The choice depends on whether you want recursive traversal, how you want to handle the results, and your Python version. Using os.walk() The os.walk() function is the classic approach for recursively iterating through directories. It yields tuples of (dirpath, dirnames, filenames)…
When you have SSH key-based authentication set up, the client will prefer it by default. This can make it difficult to test whether password authentication is working—especially after changing a password or troubleshooting login issues. Force password-only authentication Use the -o PreferredAuthentications=password flag: ssh -o PreferredAuthentications=password username@host This tells SSH to use password authentication exclusively,…
The simplest way to detect whether your Linux system booted in UEFI or BIOS (Legacy) mode is to check for the existence of the EFI firmware directory. Check for EFI Directory The /sys/firmware/efi/ directory only exists when the system has booted in UEFI mode. If it’s absent, the system is running in BIOS/Legacy mode. […
While BIOS settings are the preferred way to disable USB 3.0, you can also force USB 2.0 mode on a running Linux system by manipulating the xHCI controller’s port routing register directly using setpci. How it works Intel xHCI controllers use the XUSB2PR (xHC USB 2.0 Port Routing Register) at offset 0xd0. Setting this register…
[md] gThumb’s preferences aren’t always obvious when you’re looking through the traditional menu bar. The location depends on your desktop environment and gThumb version. ## GNOME Desktop On GNOME 3 and later, preferences are accessed through the application menu rather than the window menu: 1. Open gThumb 2. Click the application name (“gThumb”) in the…
When clients connect to your OpenWRT router via DHCP, they typically receive the router itself as the default gateway. Sometimes you need to advertise a different gateway — whether you’re running a proxy, load balancer, or multi-gateway setup on your network. This is done via DHCP option 3 (the router option in the DHCP specification)….
Chrome stores passwords encrypted in the system keyring (GNOME Keyring, KWallet, or Pass depending on your desktop environment). To export them in plain text, you’ll need to create a temporary Chrome profile with basic (unencrypted) password storage, sync your passwords from Google Cloud, then extract them from the SQLite database. Prerequisites Chrome or Chromium installed…
When troubleshooting email delivery or verifying mail server configuration, you need to look up the MX (Mail Exchange) records for a domain. On Linux, two tools handle this: host and dig. Both are reliable, though dig is generally preferred for its flexibility and cleaner output format. Using dig to query MX records The dig command…
When an NFS server goes down or becomes unreachable, client mounts can end up in a “Stale NFS file handle” state. Standard umount and umount -f commands fail, leaving you stuck with an unusable mount point and no clean way to recover without rebooting. The solution is to use umount -l (lazy unmount), which immediately…
When you need writes to one or more files to automatically go to another file, you have several options depending on your exact use case. The most common scenario is capturing output from commands, monitoring file changes, or duplicating writes across multiple destinations. Using tee for Command Output Duplication The tee command duplicates standard input…
Firefox uses a profile system to isolate settings, extensions, bookmarks, and browsing data. By default, Firefox only allows one instance per profile to run at a time—new instances redirect to the existing process. If you need multiple Firefox windows with different profiles open at once, you need to disable this behavior. The -no-remote Flag The…
Long lines in text files can be difficult to read in a terminal. Linux provides several built-in tools to wrap or fold long lines to fit your screen width, each with different strengths. Using fold — Simple Line Wrapping fold wraps lines at a specified character width: # Wrap at 80 characters fold -w 80…
[md] By default, Fedora doesn’t enable SSH access. You’ll need to install OpenSSH server, start the service, and configure your firewall to allow connections. ## Install OpenSSH Server sudo dnf install openssh-server openssh-clients The openssh-clients package provides the ssh command for connecting to other machines, while openssh-server allows incoming connections. ## Start and Enable the…
When you fork a repository on GitHub or GitLab, your copy diverges from the original as upstream maintainers merge new changes. To keep your fork current, you need to regularly sync it with the upstream repository. Setting up the upstream remote First, check your current remotes: git remote -v You’ll see origin (your fork). Add…
When you have multiple static libraries (.a files) and need to combine them into a single archive, GNU ar provides several approaches. The most straightforward method uses ar‘s MRI mode for clarity and maintainability. Using ar MRI Mode The cleanest approach is to use ar -M with an MRI script. This method is explicit and…
OpenWrt runs Dropbear as its SSH server instead of OpenSSH. While Dropbear supports RSA and modern key types, the authorized_keys file lives in a different location, which causes ssh-copy-id to fail silently. Here’s how to set up key-based authentication properly. Why ssh-copy-id doesn’t work ssh-copy-id looks for ~/.ssh/authorized_keys on the remote system, which is OpenSSH’s…
Fedora uses systemd-tmpfiles to automatically clean up temporary files and directories. By default, this includes volatile files in /tmp/, which can cause problems for applications that rely on files persisting there — like HDFS DataNodes that store their PID files as hadoop-hadoop-datanode.pid. How systemd-tmpfiles Works The systemd-tmpfiles service runs periodically (typically daily and at boot)…
systemd uses targets instead of the old sysvinit runlevels. Runlevel 3 (console mode) maps to multi-user.target. Here’s how to boot directly to console on Fedora, RHEL, Debian, Ubuntu, and other systemd-based distributions. Switch to Console Mode Immediately To switch from graphical mode to console without rebooting: sudo systemctl isolate multi-user.target This immediately stops the display…
Vim supports Xterm 256-color codes on Linux and modern terminals. Understanding the color palette and how to use it in your configuration is essential for building readable syntax highlighting schemes and custom colorschemes. The 256-Color Palette Xterm’s 256-color mode consists of: Colors 0-15: Standard ANSI colors (black, red, green, yellow, blue, magenta, cyan, white, and…
You may need to deactivate a LVM volume group to make it unknown to the kernel — typically before removing disks, migrating storage, or performing maintenance. The vgchange command handles this with the -a (or –activate) flag. Basic deactivation To deactivate a volume group named vg, use: vgchange -a n vg The -a n flag…