How to Resize a KVM Virtual Disk Expanding a VM’s storage is a common task in virtualization. The Commands Resize the image: qemu-img resize disk.qcow2 +10G Expand in Guest: Use fdisk/parted and resize2fs (ext4) or xfs_growfs (xfs) inside the VM. KVM in 2026 In 2026, QEMU/KVM remains the standard for Linux virtualization. For cloud-native environments,…
Generic Lambdas in C++ (Avoiding Concrete Types) In C++11, lambda parameters required concrete types. If you wanted a “generic” lambda, you had to wrap it in a template struct. Since C++14, we’ve had Generic Lambdas, which use auto to deduce types. The Modern Syntax (C++14/17/20) auto add = [](auto a, auto b) { return a…
How to Check for Block Special Files in Python In Linux, hardware like hard drives and SSDs are represented as “block special files” (usually in /dev). Python provides a simple way to identify them using the os module. The Pythonic Way import os import stat path = “/dev/sda” try: mode = os.stat(path).st_mode if stat.S_ISBLK(mode): print(f”{path}…
How to Create and Open a File in C (Read/Write Mode) In C, the fopen function handles file creation and opening. To get read/write access with creation, you need the right combination of “mode” strings. The Code FILE *fp = fopen(“myfile.txt”, “a+”); // ‘a+’ opens for reading and appending. // It creates the file if…
The problem is with ssh that makes a quoted string to more than one if there are spaces. For example, ssh user@host cmd “my string” The cmd on host will be executed like cmd my string rather than cmd “my string” It will only work if the string is escaped like ssh user@host cmd my…
In many text processing tasks, we often need to check if a given string starts with a specific substring. In this article, we will demonstrate how to achieve this using the std::string::compare() function from the C++ Standard Library. The compare() function has several overloads, but the one of interest for our purpose is: int compare(size_type…
How to split and iterate a string separated by a specific character in C++? For example, “a string separated by space” by ‘ ‘=> [“a”, “string”, “separated”, “by”, “space”] and “a,string,separated,by,comma” by ‘,’ => [“a”, “string”, “separated”, “by”, “comma”] C++ standard library’s getline() function can be used to build a function. getline() can accept a…
How to Generate a Secure Password in the Linux Shell Generating strong, random passwords from the command line is a vital skill for sysadmins. In 2026, we have more tools than ever to do this securely without leaving the terminal. Method 1: openssl (Reliable & Standard) openssl rand -base64 12 generates a 12-character random string….
How to operator[] access element in a const map in C++? For example, the compiler will report error on this piece of 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…
Vim seems not indent C++11 lambas very well. How to make Vim indent C++11 lambdas correctly? For this following program, Vim indents it as #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) -> std::string { if (s == “one”) {…
It seems Thunderbird sends out my private/lan IP to the SMTP server. For example, in an Email sent out by Thunderbird, the header contains Received: from [192.168.1.2] (example.com [1.2.3.4]) by mail.example.com (Postfix) with ESMTPSA id 92CD297DEA; It is fine that the SMTP server records the public IP (1.2.3.4) as it is what it sees. But…
How to list start and end of a partition by the sectors in parted on Linux? The default behavior seems be listing the start and end by bytes in parted. # parted /dev/sdc print Model: Innostor IS888 ext. HDD (scsi) Disk /dev/sdc: 2000GB Sector size (logical/physical): 512B/512B Partition Table: gpt Disk Flags: Number Start End…
Evolution seems wrap long lines automatically in “Plain Text” mode. How to make Evolution not wrap lines in composed Emails? Evolution does not have (so far) “Flowing Text” mode where “the text is soft broken at the composer edge, but those soft breaks aren’t translated to hard breaks when the mail is sent” ( Reference:…
How to Enable Email Address Auto-completion in Evolution GNOME Evolution is one of the most powerful email clients on Linux, but its auto-completion can sometimes feel “hidden” compared to webmail clients. How to Ensure It Works Check Contacts: Evolution auto-completes from your “Personal” and “On This Computer” address books. Enable Autocomplete: Go to Edit ->…
How to Search Bash History Effectively The “Up Arrow” is slow. In 2026, every power user relies on incremental history search to recall complex commands from the past. The Magic Shortcut: Ctrl + R Press Ctrl + R. Start typing a keyword from the command you remember (e.g., “docker”). Bash will show the most recent…
How to Apply Email Sort Order to All Folders in Evolution By default, Evolution remembers the sort order (e.g., by Date, Sender, or Subject) for each folder individually. If you want a consistent view across your entire mailbox, you have to set it globally. The Steps Open Evolution and go to Edit -> Preferences. Select…
How to iterate all dirs and files in a dir in C++? To open a dir, we can use opendir() to open a directory stream. DIR *opendir(const char *name); Then we can use readdir() to iterate the directory stream. struct dirent *readdir(DIR *dirp); Here is an example C++ program using these 2 library functions. #include…
How to Check CPU Frequency on iOS Unlike Android or Linux, iOS is a “walled garden” that doesn’t provide direct access to hardware sensors like CPU clock speeds through the standard UI. However, there are ways to peek under the hood. The Developer Way: Xcode Instruments If you are an iOS developer, you can connect…
How to Get a File’s Modification Time in C on Linux The stat system call is the standard way to retrieve file metadata. The Code #include <sys/stat.h> struct stat st; stat(“path/to/file”, &st); printf(“Mtime: %ld”, st.st_mtim.tv_sec); C Programming in 2026 In 2026, while stat is still the go-to, modern C code (C11/C17) often uses struct timespec…
How to “Un-ignore” Files in Git Sometimes you have a global gitignore rule (like ignoring all *.log files) but need to track one specific exception. Git allows you to “negate” a pattern using the ! character. The Negation Pattern In your .gitignore file: # Ignore all log files *.log # But DO track this one…