Expanding a VM’s storage is a routine operation in KVM environments. The process has two distinct phases: expanding the raw disk capacity and then growing the partitions and filesystems to use that space. Resizing the Disk Image The first step is to increase the virtual disk size using qemu-img: qemu-img resize disk.qcow2 +10G This adds…
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…
In C++11, lambda parameters required concrete types. Creating a truly generic lambda meant wrapping the logic in a template struct — awkward and verbose. C++14 introduced generic lambdas using auto for parameter deduction, eliminating this friction entirely. Basic Generic Lambda Syntax The simplest approach uses auto in lambda parameters: auto add = [](auto a, auto…
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 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,…
C++20 introduced std::string::starts_with(), which is the most straightforward way to check if a string begins with a specific substring: #include <iostream> #include <string> int main() { std::string text = “big string here…”; std::cout << std::boolalpha; std::cout << text.starts_with(“big”) << std::endl; // true std::cout << text.starts_with(“small”) << std::endl; // false std::cout << text.starts_with(“big string”) << std::endl;…
Splitting strings by a delimiter is a common task in systems programming. C++ doesn’t provide a built-in split function like Python, but you can implement one efficiently using the standard library. Using std::istringstream and getline() The standard approach uses std::istringstream with std::getline(). The getline() function accepts a delimiter parameter, allowing you to extract tokens until…
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…
Using operator[] on a const map will fail to compile. This code: #include <iostream> #include <string> #include <map> std::int64_t count(const std::map<std::string, std::int64_t>& map) { return map[“one”] + map[“two”]; } int main() { std::map<std::string, std::int64_t> map = { {“one”, 1}, {“two”, 2} }; std::cout << count(map) << std::endl; return 0; } produces a compiler error: error:…
Vim’s default indentation can mangle C++11 lambdas, treating them like nested blocks instead of closures. The lambda body gets indented too far relative to the enclosing statement. The Problem Given this code: #include <iostream> #include <string> #include <vector> #include <algorithm> int main() { std::vector<std::string> strs({“one”, “two”}); std::vector<std::string> newstrs; std::transform(strs.begin(), strs.end(), std::back_inserter(newstrs), [](const std::string& s) ->…
Thunderbird can leak your LAN IP address in SMTP email headers, even though the mail server itself only sees your public IP. This happens because Thunderbird sends its local IP during the HELO/EHLO handshake with the SMTP server, and that information gets recorded in the email header. For example, you might see: Received: from [192.168.1.2]…
GNOME Evolution’s email address auto-completion works by querying your local address books and, optionally, external sources. Here’s how to get it working properly. Check Your Address Books Evolution pulls auto-completion suggestions from multiple sources: Personal address book (local contacts you’ve added) On This Computer (system-wide contacts) Synced contact sources (Google, CalDAV, CardDAV, LDAP) To see…
By default, parted displays partition boundaries in bytes. To view start and end positions in sectors instead, you need to set the unit explicitly using the unit command. Using the unit command The unit subcommand in parted sets the display unit for locations and sizes. The syntax is straightforward: parted /dev/sda unit s print The…
Evolution automatically wraps long lines in Plain Text mode, which can be frustrating if you need to preserve line breaks exactly as you’ve written them. Unlike some email clients, Evolution doesn’t support “soft wrapping” where text reflows visually in the composer but sends without hard line breaks. Using External Editor The most straightforward approach is…
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….
Evolution stores sort preferences individually per folder by default. If you want emails consistently sorted across your entire mailbox, you need to set a global default. Steps Open Evolution and navigate to Edit → Preferences Go to Mail Preferences → General Locate the Default Sorting section Choose your preferred Sort by option (Date Received, Subject,…
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&…
iOS deliberately restricts direct access to CPU clock speeds through its public APIs — Apple treats this as implementation detail rather than user-facing information. That said, there are legitimate approaches depending on your needs. Xcode Instruments for Developers If you’re developing for iOS, connect your iPhone to a Mac with Xcode and use Instruments to…
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…
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…