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…
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…
SPF (Sender Policy Framework) is a DNS-based authentication mechanism that helps prevent email spoofing by specifying which mail servers are authorized to send emails on behalf of your domain. If your domain is hosted with DreamHost, you’ll need to add an SPF record to your DNS configuration. Understanding SPF Records An SPF record is a…
Limiting CPU resources for individual users is essential for preventing resource exhaustion, maintaining fair system performance, and isolating workloads. Whether you’re managing multi-user systems, shared hosting environments, or need to constrain specific applications, Linux provides several proven methods. Using cgroups (Control Groups) Modern cgroups v2 offer the most flexible and reliable approach. Most distributions use…
The fastestmirror plugin automatically selects the fastest package mirror for your system. While useful, you might want to disable it if you’re experiencing slow mirror detection, prefer a specific mirror, or troubleshoot package manager issues. The plugin is provided by yum-plugin-fastestmirror (on older EL7 systems) or as part of DNF’s core functionality (EL8+). Unlike older…
If you’re seeing PHP errors like Class ‘DOMDocument’ not found, your PHP installation is missing the XML extension. This is common after migrating sites or fresh installations where the base PHP package doesn’t include DOM support out of the box. Install php-xml The solution is straightforward — install the php-xml package: sudo dnf install php-xml…
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…
When you need to break up a large gzip file into smaller chunks, you have several practical options depending on your constraints. Using zcat with split The most straightforward approach is to decompress the gzip file and split it simultaneously: zcat large_file.gz | split -b 100M – chunk_ gzip chunk_* This decompresses large_file.gz, pipes it…
When you modify /etc/fstab, systemd doesn’t automatically pick up the changes. You need to explicitly tell systemd to reload its configuration and apply the new mount points. The Basic Reload To force systemd to recognize changes in /etc/fstab, run: sudo systemctl daemon-reload This tells systemd to re-read all unit files and configuration, including the mounts…
Date comparison is one of the most common operations in SQL queries, whether you’re filtering orders, analyzing logs, or generating reports. The approach varies slightly across database systems, but the underlying principles remain consistent. Basic Date Comparison The simplest form uses standard comparison operators against a date string in YYYY-MM-DD format: SELECT * FROM orders…
Atomicity is fundamental to distributed filesystems. When multiple processes across a cluster access the same files, operations must either complete fully or not at all—no partial states. HDFS provides specific atomic guarantees that applications can rely on for implementing distributed locks and coordinating access patterns. What HDFS Guarantees as Atomic As of Hadoop 3.2.1 (and…
In PHP, STDOUT and STDERR are standard output streams that handle different types of output. STDOUT carries normal program output, while STDERR carries error messages and diagnostic information. Properly directing output to the correct stream is essential for building reliable scripts and applications. Using fwrite() with Stream Handles The most straightforward approach uses fwrite() with…
Understanding file descriptors is fundamental to shell scripting. By default, your shell has three standard streams: STDOUT (FD 1): Standard output, where commands print results STDERR (FD 2): Standard error, where commands print errors and diagnostics STDIN (FD 0): Standard input, where commands read data Basic Output Print to STDOUT: echo “This goes to stdout”…
Go provides straightforward ways to write to standard output and standard error streams. Understanding when and how to use each is essential for building robust applications, especially in containerized and cloud environments where log separation matters. Using the fmt Package The fmt package is the most common approach for printing to STDOUT: package main import…
Getting a process’s parent process ID (PPID) is useful for monitoring, debugging, and process management tasks. Go provides straightforward ways to access this information across different platforms. Using the os Package The simplest approach is the os package, which works on Unix-like systems: package main import ( “fmt” “os” ) func main() { ppid :=…
To retrieve the parent process ID (PPID) of the current running process, use the getppid() system call. This is the standard and portable approach on Unix-like systems including Linux. #include <stdio.h> #include <unistd.h> int main() { pid_t ppid = getppid(); printf(“Parent process ID: %d\n”, ppid); return 0; } Compile and run: gcc -o get_ppid get_ppid.c…