Kernel parameters often need to be passed to Xen DomUs during boot or for troubleshooting. Common scenarios include booting into single-user mode for recovery, enabling kernel debugging, or adjusting memory/CPU settings at runtime. Using the extra parameter The simplest method is passing kernel parameters via the extra= option when creating or starting a DomU. For…
To convert a PostScript file to PDF suitable for publishing, use ps2pdf from the Ghostscript suite: ps2pdf -dPDFSETTINGS=/printer file.ps file.pdf The /printer setting produces high-quality output appropriate for publication. Other available quality settings include: /screen — lowest quality, smallest file size /ebook — medium quality, reasonable file size /printer — high quality, suitable for printing…
By default, closing the last open tab closes the entire Chrome browser window. If you want Chrome to stay open and display a new tab instead, you’ll need to either use an extension or adjust your workflow. Using an Extension The Last Tab Standing extension is the most straightforward solution. It intercepts the close action…
When you first use git on a machine, you’ll need to configure your identity. Git uses these credentials to author your commits: git config –global user.name “Your Name” git config –global user.email you@example.com These settings are stored in ~/.gitconfig and apply to all repositories on your system. Verifying your configuration Check what you’ve set: git…
When working with relative paths in Linux, you often need the absolute path for scripting, logging, or passing to other programs. Several tools can resolve this, each with different strengths. Using readlink The readlink command is the traditional tool for this job. The -f flag follows symlinks and resolves the path to its absolute form:…
Dropbox on Linux has two main approaches: the official daemon (headless) or the sync client with GUI. Which you choose depends on your use case. Official Dropbox Daemon (Recommended for Servers) The daemon is lightweight and works well on headless systems. Download and extract it: cd ~ && wget -O – “https://www.dropbox.com/download?plat=lnx.x86_64” | tar xzf…
Archiving or copying a 1TB sparse file containing only 32MB of actual data is impractical with naive approaches—you’ll waste time and I/O bandwidth copying zeros. The solution is using SEEK_HOLE and SEEK_DATA flags with lseek(), which allow tools to skip over hole regions entirely. How SEEK_HOLE and SEEK_DATA work The Linux kernel provides two additional…
When you mmap() a range larger than your system’s total physical memory plus swap, the kernel normally reserves swap space to back the mapping. If that reservation would exceed available swap, mmap() fails with ENOMEM. The MAP_NORESERVE flag lets you bypass this reservation requirement. Understanding the Default Behavior By default, when you call mmap() with…
A hard link is an additional directory entry pointing to the same inode as the original file. Unlike symbolic links, hard links share the same inode number and have identical permissions, ownership, and content. To find all hard links to a file, you need to locate every directory entry with the same inode. Using find…
LVM (Logical Volume Management) abstracts physical storage into logical volumes, giving you flexibility to resize filesystems, snapshot data, and manage disk space without downtime. It sits between your physical disks and the filesystems you mount. The three core LVM concepts are: Physical Volumes (PVs): Physical disks or disk partitions Volume Groups (VGs): Collections of PVs…
When you need to verify that two Linux systems can communicate over a specific protocol and port, you have several solid options. Let’s cover the most practical approaches. Using nc (netcat) The nc command remains a reliable choice for quick connectivity tests. It’s widely available and requires no special setup. TCP connection test To listen…
Evolution is a full-featured personal information management suite that handles email, contacts, calendars, and tasks. It includes enterprise features like native Microsoft Exchange support and integrates deeply with GNOME’s ecosystem. To troubleshoot issues, migrate data, back up configurations, or secure your setup, you need to know where Evolution stores everything. Evolution follows the XDG Base…
NFSv4 significantly simplifies network exposure compared to NFSv3. Where NFSv3 requires managing multiple dynamic ports (mountd, statd, lockd), NFSv4 uses only port 111 (rpcbind) and port 2049 (NFS). This makes firewall configuration and port forwarding straightforward. For production environments, consider implementing Kerberos authentication (krb5, krb5i, or krb5p) instead of relying solely on network-based access control….
When you need to display data on point-of-sale receipts that isn’t available in the standard receipt designer, you’ll need to create a custom field. This involves work in both Dynamics 365 (the backend) and the Retail SDK (the POS application layer). This walkthrough covers adding a custom field—using item barcodes as an example—though the pattern…
Hibernate Envers is a proven auditing framework that automatically tracks changes to JPA entities without cluttering your domain model with logging code. It stores historical data in separate audit tables and lets you query entity states at any point in time. Why Use Hibernate Envers Envers handles the mechanics of change tracking transparently: Audits all…
ASP.NET Core remains one of the most efficient frameworks for building scalable web applications. This guide walks through deploying an ASP.NET Core MVC application to Azure App Service using Visual Studio — the quickest path from local development to production. Prerequisites You’ll need: An active Azure subscription (free tier accounts work fine for testing) Visual…
Before encoding instructions, you need to understand the two assembly syntaxes you’ll encounter—they differ fundamentally in operand order and addressing format. Intel syntax (Intel/AMD manuals): Operand order: destination, source Memory addressing: [base+offset] Example: add r8, [rdi+0xa] AT&T syntax (GNU toolchains on Linux): Operand order: source, destination Memory addressing: offset(%base) Example: addq 0xa(%rdi), %r8 For most…
The Secondary NameNode periodically merges the fsimage and edits log files to keep the edits log manageable and consolidate metadata. When this checkpointing fails, you’ll see errors like: ERROR org.apache.hadoop.hdfs.server.namenode.SecondaryNameNode: Exception in doCheckpoint java.io.IOException: Inconsistent checkpoint fields. This typically indicates a mismatch between the NameNode and Secondary NameNode metadata states, often from unclean shutdowns or…
When you need to debug kernel behavior without full instrumentation frameworks, module parameters offer a pragmatic shortcut. Rather than immediately reaching for perf, kprobes, or eBPF, you can add simple toggles and state tracking directly in the code you’re investigating, then control them at runtime through sysfs. Frameworks like perf, kprobes, and eBPF are powerful…
Call forwarding redirects incoming calls to another number when you’re unavailable or without coverage. It’s a carrier-level feature managed through iOS Settings, but actual support and behavior depend entirely on your carrier’s implementation. Enable call forwarding Open Settings → Phone Tap Call Forwarding Toggle the switch to On Enter the phone number where calls should…