The up arrow works, but it’s tedious for finding commands from weeks ago. Bash offers several practical methods to search your history efficiently. Built-in Incremental Search: Ctrl + R Press Ctrl + R to enter reverse-search mode. Type any part of the command you remember: (reverse-i-search)`docker’: docker ps -a Bash displays the most recent match….
If you’ve tried ssh root@my-server and got a “Permission denied” error, it’s not a bug—it’s a security feature. This behavior is standard across all modern distributions. Why Root SSH Login is Disabled By default, the PermitRootLogin directive in /etc/ssh/sshd_config is set to prohibit-password or no. This prevents direct root access over SSH regardless of whether…
For iterating through directories and files in C++, you have several options depending on your needs and C++ standard version. Using <filesystem> (C++17 and Later — Recommended) The modern approach uses std::filesystem, which is cleaner, safer, and handles cross-platform differences for you: #include <filesystem> #include <iostream> #include <string> namespace fs = std::filesystem; int ListDir(const std::string&…
The stat() system call is the standard way to retrieve file metadata on Linux, including modification time (mtime). It’s fast, portable, and gives you access to nanosecond-precision timestamps. Basic Approach with stat() #include <sys/stat.h> #include <stdio.h> struct stat st; if (stat(“path/to/file”, &st) == -1) { perror(“stat failed”); return 1; } printf(“Mtime (seconds): %ld\n”, st.st_mtime); printf(“Mtime…
Stripping newlines from strings is common when processing text input, especially from files or network streams. Here are the practical approaches. Using erase() with std::remove() The most efficient method combines std::remove() and erase() — this is the erase-remove idiom: #include <iostream> #include <algorithm> #include <string> int main() { std::string input{“line 1\n\n\nline 3\nline 4”}; std::cout <<…
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…
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…
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:…
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…
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…
Password-less SSH login is faster, more secure, and essential for automation. Combining it with remote command execution lets you run tasks on servers from your local machine without interactive authentication. Setting Up SSH Key-Based Authentication Generate SSH Keys First, generate an ED25519 key pair on your local machine (A): ssh-keygen -t ed25519 -C “user@hostname” -f…
The diff command on Linux is standard, but Windows doesn’t ship with an equivalent by default. You have several solid options depending on whether you prefer command-line or GUI tools. Command-Line Alternatives If you want a command-line experience similar to Linux diff: Windows PowerShell (built-in, Windows 10+): Compare-Object (Get-Content file1.txt) (Get-Content file2.txt) For more diff-like…
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…
I/O schedulers in Linux sit between application requests and physical disk hardware, deciding the order in which I/O operations execute. The fundamental difference between work-conserving and non-work-conserving schedulers comes down to how they handle idle periods. Work-Conserving Schedulers A work-conserving scheduler must dispatch a pending I/O request whenever one exists, regardless of physical disk positioning….
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…
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…
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…