Sometimes you have a global gitignore rule—like ignoring all *.log files—but need to track one specific exception. Git lets you negate patterns using the ! character. # Ignore all log files *.log # But DO track this one specific file !important.log Pattern matching is evaluated top-to-bottom, and the last matching pattern wins. Your negation rule…
You can extract and display a single file’s content from a tar archive without unpacking the entire archive using tar‘s standard output option. Basic Syntax tar -xOf archive.tar.gz path/to/file The key flags are: -x: Extract files from the archive -O (capital O): Write extracted files to standard output instead of disk -f: Specify the archive…
By default, make executes the first target it encounters in your Makefile. This works fine for simple projects, but as Makefiles grow and you have multiple build configurations, deployment targets, and test suites, you’ll need explicit control over which target runs by default. The .DEFAULT_GOAL Variable The cleanest way to change the default target is…
Determining whether a path points to a directory or regular file is a common task in system programming. You need to stat the path and inspect the file mode. Using lstat() and stat macros The lstat() system call retrieves file metadata into a struct stat. For a given path, you can use the standard macros…
Identifying which ports a specific process is using comes up regularly in debugging, security audits, and infrastructure management. Here are the practical methods. Using ss The ss command is the modern standard for socket inspection: ss -tlnp | grep <PID> This shows listening TCP sockets (-t for TCP, -l for listening). Add -u if you…
Use ipcs to see all IPC resources on your system: ipcs -m This shows System V shared memory segments with details like: SHMID: The segment identifier OWNER: User who created it PERMS: Permissions (octal format) BYTES: Size in bytes NATTCH: Number of processes attached For a more compact view focused on just what you need:…
Retrieving hardware serial numbers is essential for inventory management, warranty tracking, and identifying physical servers across your infrastructure. The standard approach uses dmidecode, which reads the system’s DMI (Desktop Management Interface) data. Using dmidecode First, install the tool: sudo apt-get install dmidecode For Rocky Linux, RHEL, and derivatives: sudo dnf install dmidecode Then query the…
You need to detect whether STDERR (file descriptor 2) is connected to a terminal or redirected to a file or pipe. This is useful for conditional logging, color output, or error handling that depends on the output destination. Using file descriptor tests The primary method is the -t test operator, which checks if a file…
Accurate system time is critical for log timestamps, security operations, certificate validation, and coordinating across distributed systems. Modern Linux distributions handle time synchronization automatically, but you’ll occasionally need to set the time manually. Using timedatectl The standard tool for time management on systemd systems is timedatectl. Check your current time and synchronization status: timedatectl status…
When you call os.makedirs(path, mode=0o777) in Python, the resulting directory often won’t have the permissions you expect. The mode argument gets masked by the process’s umask, which removes certain permission bits before applying them to the filesystem. Your umask acts as a filter. If your umask is 0o022 (common on many systems), it removes write…
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…
When you access a non-existent key in a Python dictionary, you’ll hit a KeyError. There are several approaches to handle this gracefully depending on your use case. The .get() Method The simplest and most common approach: value = my_dict.get(‘key’, ‘default_value’) This returns the value if the key exists, or the default value if it doesn’t….
alien is a straightforward package converter available in EPEL that handles conversion between .deb, .rpm, Slackware, and other package formats. This is useful when you need to install Debian packages on RPM-based systems. Prerequisites You need EPEL (Extra Packages for Enterprise Linux) enabled. On CentOS 7, 8, or Rocky Linux 8+: sudo dnf install epel-release…
GNOME 3 and GNOME Classic don’t provide built-in autohide functionality for the top panel or taskbar. Unlike some lightweight desktop environments, this feature isn’t available through the standard settings or extensions in recent GNOME versions. If you need panels that automatically hide when applications are running, you have several options: GNOME Extensions (limited approach) While…
The NameNode in HDFS maintains the filesystem namespace in memory. The Secondary NameNode (or Checkpoint Node in HA setups) periodically merges the namespace image (fsimage) with the edit logs to create a new checkpoint. Understanding how to force this process is essential for cluster maintenance and recovery operations. How Checkpointing Works The checkpoint process combines…
Filesystem corruption occasionally happens. When it does, you need fsck to run before the system fully mounts its filesystems. Here’s how to force a filesystem check during the next boot. Using touch to Mark Filesystems The traditional method is to create /forcefsck: sudo touch /forcefsck sudo reboot On the next boot, the system will check…
Interrupts are fundamental to how your Linux system handles hardware and software events. Monitoring them in real-time helps identify performance bottlenecks, device driver issues, and CPU load imbalances. Here’s how to check interrupts effectively. Quick Live Monitoring with /proc/interrupts The simplest approach is reading /proc/interrupts directly: cat /proc/interrupts This shows a snapshot of interrupt counts…
By default, Python buffers stdout when it’s not connected to a terminal — typically when you redirect output to a file, pipe to another command, or run inside a container. This buffering can hide output until the buffer fills or the program exits, making debugging and log monitoring difficult. Using the flush parameter The simplest…
Achieving high performance in virtualized environments requires careful tuning of kernel parameters, CPU idle states, and hypervisor settings. The goal is to reduce context switching overhead, minimize latency, and keep vCPUs busy rather than cycling through low-power states. Kernel Boot Parameters Add these parameters to your kernel boot line in /etc/default/grub: intel_idle.max_cstate=0 processor.max_cstate=0 idle=poll intel_pstate=disable…
CPU affinity pins a process to specific CPU cores, reducing context switches and improving cache locality. This matters when you need consistent latency or want to isolate workloads on multi-core systems. Using taskset taskset is the standard tool for setting CPU affinity on running processes. The basic syntax: taskset -p -c 0,1,2 <pid> This binds…