The built-in pdb module is Python’s equivalent to gdb — a command-line debugger that lets you step through code, set breakpoints, inspect variables, and control execution flow. It’s essential for server-side debugging and situations where IDE graphical debuggers aren’t available. Starting a pdb Session Run a script through pdb directly: python -m pdb prog.py arg1…
iptables remains the standard firewall interface across most Linux distributions, though it’s technically a compatibility layer over nftables. Whether you’re managing legacy systems or prefer the familiar syntax, here’s what you need to know. Basic Command to Open a Port The fundamental syntax to allow inbound traffic on a specific port: sudo iptables -A INPUT…
Intercepting traffic before normal routing decisions requires understanding packet flow through iptables chains. If you need incoming packets to bypass the INPUT chain and process through FORWARD instead, you’ll use the PREROUTING chain with Destination NAT (DNAT). Packet Flow Through iptables When a packet arrives at your system, it traverses these chains in order: PREROUTING…
In Linux, everything is a file—including hardware devices. Block devices like disks, SSDs, and USB drives appear as files in /dev and handle I/O in fixed-size blocks. You need reliable ways to detect them in your Python scripts, especially when automating storage operations. Using pathlib (Recommended) Python 3.4+ provides pathlib.Path.is_block_device(), which is the modern standard:…
When you need to load configuration files, data files, or assets relative to your script’s location, the current working directory won’t work — it depends entirely on where you called the script from, not where the script actually lives. Use pathlib.Path: from pathlib import Path # The directory where the script lives script_dir = Path(__file__).resolve().parent…
The stat() system call is the traditional approach for checking file existence: #include <sys/stat.h> int file_exists(const char *path) { struct stat buffer; return (stat(path, &buffer) == 0); } This returns 1 if the file exists, 0 otherwise. The stat() call fills the buffer with file metadata, but when checking existence alone, you’re mainly interested in…
The Control Center in iOS provides the quickest way to toggle wireless connections. Here’s what you need to know across iOS versions. Accessing Control Center On modern iPhones with Face ID (iPhone X and later), swipe down from the top-right corner of the screen. On iPhones with a Home button (iPhone 8 and earlier), swipe…
MPlayer reached end-of-life in 2010 and hasn’t received updates since. If you’re still using it, you’re missing years of improvements in video decoding, filtering, and performance. For new projects, use mpv instead—it’s the maintained fork that incorporates MPlayer’s codebase with significant enhancements. That said, if you’re stuck maintaining legacy MPlayer setups, here’s how to optimize…
/dev/shm is a tmpfs mount that allocates storage from your system’s RAM rather than disk. It’s commonly used for inter-process communication (IPC), shared memory segments, and temporary data that needs low-latency access. By default, Linux allocates half your total RAM to /dev/shm, but you’ll often need to adjust this for specific workloads. Checking Current Size…
When managing packages on RHEL, CentOS, AlmaLinux, or Fedora, you sometimes need to prevent a package from being installed or updated from a particular repository. This is useful when multiple repos provide the same package and you want to control which version gets pulled in. Repository-specific exclusions with DNF Modern systems use DNF (which supersedes…
“Cleaning” history usually means rewriting it to remove large files, sensitive data, or to squash messy commits into logical units. This is destructive—it rewrites history and affects anyone who’s cloned the repo. Only do this on branches you control or coordinate with your team first. git filter-repo: The Standard Tool git filter-repo replaced the deprecated…
In XML, CDATA (Character Data) sections let you include text without worrying about XML special characters. Everything inside <![CDATA[ and ]]> is treated as literal text — no parsing, no entity references. This is useful for embedding code snippets, scripts, or any content with lots of <, >, or & characters. The catch: you can’t…
On Linux, block special files represent hardware devices like hard drives, SSDs, and other block devices. They’re typically found in /dev and can be identified using Python’s stat module combined with os.stat(). The Standard Approach import os import stat path = “/dev/sda” try: mode = os.stat(path).st_mode if stat.S_ISBLK(mode): print(f”{path} is a block device”) except FileNotFoundError:…
When you need to open a file for both reading and writing, creating it if it doesn’t exist, C++ offers several approaches. The choice depends on your project’s requirements and how much control you need over the process. Using std::fstream The most straightforward modern approach uses std::fstream, part of the standard library: #include <fstream> std::fstream…
When passing quoted strings through SSH, shell quoting rules can cause unexpected behavior. The classic issue: ssh user@host cmd “my string” On the remote host, this executes as: cmd my string Instead of treating “my string” as a single argument, the shell splits it. This happens because quotes are processed by your local shell first,…
The Linux command readlink -m resolves a path to its absolute, canonical form, following all symlinks and resolving .. and . components. Python provides several ways to do this, depending on your needs and Python version. Using pathlib.Path.resolve() The modern standard approach uses pathlib: from pathlib import Path canonical_path = Path(“./../folder/./file.txt”).resolve() print(canonical_path) Path.resolve() returns an…
Generating secure, random passwords is a fundamental task for sysadmins. You have several reliable options depending on your use case and environment. openssl (most portable) The simplest and most widely available method: openssl rand -base64 12 This generates a 12-character base64-encoded string. Adjust the number to change length — openssl rand -base64 32 gives you…
Python’s str.split() method splits a string by a separator and returns a list. Here are the common patterns: “a string separated by space”.split() # [‘a’, ‘string’, ‘separated’, ‘by’, ‘space’] “a,string,separated,by,comma”.split(“,”) # [‘a’, ‘string’, ‘separated’, ‘by’, ‘comma’] Note that calling split() without arguments splits on any whitespace and automatically removes empty strings. Handling consecutive separators When…
Rocky Linux 9 and later distributions use FirewallD as the default firewall management tool. However, if you need direct control over iptables and ip6tables rules, you can disable FirewallD and use the iptables-services package to restore your rules at boot. Install and Configure iptables-services Start by installing the iptables-services package: dnf install iptables-services Create the…
[md] PHP upload limits are controlled through the php.ini configuration file. On Ubuntu/Debian systems, the file location depends on your PHP version: /etc/php/8.3/apache2/php.ini # PHP 8.3 /etc/php/8.2/apache2/php.ini # PHP 8.2 /etc/php/8.1/apache2/php.ini # PHP 8.1 To find your actual PHP version and configuration path: php -i | grep “Loaded Configuration File” ## Key Configuration Directives Three…