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VM Setup Part 2: QEMU

Previously, I decided to set up a headless VM orchestrator for daily driving and gaming. In general, installing a minimal Debian and QEMU is fairly straightforward, but the devil is in the details. Here are my notes on the process. Overall Setup The machine is a laptop. The built-in display is connected to the iGPU, and an external display is connected to the dGPU. I prefer to use only the external display; the built-in one is rarely used. I have two VMs: one as a daily driver and the other for gaming. Both have GPU passthrough. Only one runs at a time. Resources Reserved for the Host CPU: 1 core, 2 threads. RAM: 2GB (typical usage is around 500MB). Disk: 32GB. The OS only needs ~2GB, but I need extra space for cache, log, OS images, etc. CPU The main QEMU process and IO thread should be pinned to the host CPUs. vCPU threads should be pinned to the CPUs reserved for the VM. CPU pinning cannot be done through QEMU command-line arguments. I had to talk to the QEMU process via QMP...
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Exploring Gaming VM Setup (Part 1)

For years, I've been playing games and doing everything else on the same PC. Hoever, after a recent positive experience with Qubes OS, I no longer feel comfortable keeping my games, passwords, and other stuff all in the same place. Because of this, I decided to change my gaming setup. My requirements are: Performance. Gaming should be functional and playable. Isolation. At a minimum, game binaries should not have access to my other files. Quick Switch. I need to be able to switch between gaming and non-gaming easily. Single Display. All my workflows should be performance well on a single display. I do have a secondary display, but I want to rarely use it. So, here goes my adeventure. Option 1: Dual Boot This is the classic solution, which sounds boring but almost always works. Performance: Good. All operating systems have direct access to physical hardware. Isolation: OK-ish, each OS technically has access to all data from other OSes. Disk encryption and Secure Boot can mitigate th...
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Solving LVM Detection Failures in GRUB After a Force Shutdown

After a routine system update and an unfortunate hang that required a hard reset, my Linux machine refused to boot. Instead of the familiar login prompt, I was greeted by a cryptic GRUB error:  error: no cryptodisk module can handle this device. My setup uses LUKS2 + LVM. From the GRUB rescue shell, I could actually decrypt the LUKS container. But once decrypted, GRUB completely failed to detect any LVM volumes. It simply acted as if the LVM structure didn't exist. Meanwhile, if I boot it from a Live Rescue USB, everything worked perfectly. I could open the LUKS container, and the volume group appeared immediately. Tools like  vgck  and  pvck  reported no issues. After a length discussion with AI, eventually I found the magical commands: vgcfgbackup -f lvm_backup.txt <vg_name> vgcfgrestore -f lvm_backup.txt <vg_name> After running these commands and rebooting, GRUB recognized the LVM volumes immediately, and I was back in my system. Supposedly this f...
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Notes on a Tricky Linux Installation: Qubes OS and Windows

I recently tried to install Qubes OS alongside an existing Windows installation. It turned out to be surprisingly difficult—way harder than my last attempt—likely due to a combination of my encrypted  /boot  setup and older hardware. Here are some notes from the process. Shrinking an NTFS Volume I needed to free up some space from a Windows NTFS volume. Normally, this just takes a few clicks in Disk Management. This time, however, Windows reported a "shrinkable volume" that was suspiciously small. Following  this answer , I tried the standard fixes: Disabled hibernation ( powercfg /h off ) Disabled the pagefile Disabled system protection This increased the shrinkable volume a bit, but nowhere near the actual free space left on the partition. Digging into the Windows Application logs in Event Viewer, I finally found the culprit:  The last unmovable file appears to be: \$Mft::$DATA . It turns out  $Mft  is a special block in NTFS that cannot be easily moved, ...
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Refined Boot for Qubes OS: Minimal USB Key, Dual Boot, Secure Boot

I've been running Qubes OS on Machine A alongside Windows for a while. My setup involved storing the unencrypted  /boot  partition and the LUKS header on an external USB drive. Recently, I planned to install Qubes on Machine B, also in a dual-boot configuration. However, the complexity jumped significantly: Machine B has Secure Boot enabled because BitLocker requires it. On previous installs, I grew tired of toggling Secure Boot in the BIOS every time I switched operating systems. I only have one USB drive. Managing separate  /boot  partitions for two different Qubes installations on a single thumb drive is messy. After some experimentation, I found a way to solve both problems. Sharing One USB Drive for Multiple Qubes Installations The solution is elegant: Don't store  /boot  on the USB drive. Instead, move  /boot  to the encrypted internal disk partition. The USB drive's only job is to unlock that partition and hand over control to the system. O...
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Writing Sudoku Solvers

After writing a Nonogram solver, I decided to tackle a Sudoku solver to practice Rust. My goal wasn't just to support classic Sudoku rules, but also to handle variants like Thermometer, Arrow, and Cage etc. 1. Brute Force It is fairly easy to write a brute force or backtracking algorithm. This approach is sufficient for most classic Sudoku puzzles, but it becomes unbearably slow as soon as variant rules are introduced. I considered this step a warmup—a baseline to improve upon. 2. Constraint Propagation Here, I tried to introduce "logical thinking" to the algorithm. I used  u16  as a bitmask to represent the possible values of a cell. Whenever a cell's state changes (due to guessing, backtracking, or propagation), the algorithm consults all constraints to eliminate impossible candidates. While Nonogram is technically an NP-Complete problem, in practice, my constraint-propagation solver (without guessing) can solve almost all puzzles found online. I’ve only seen one ex...
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An Adventure with Qubes OS

I've been experimenting with Qubes OS on my new laptop and wanted to share some notes on the experience. Hardware Overall, Qubes OS works quite well on my hardware. Aside from typical issues like deep sleep, speaker performance, and touchpad scroll speed, the experience has been smooth. I particularly like that I can boot directly from a microSD card. This allowed me to move the  /boot  partition to the card while completely disabling USB access in  dom0  for better security. Detached  /boot  and LUKS Header Moving  /boot  and the LUKS header to a microSD card is a fun project, but it has some drawbacks: I have to remember to mount  /boot  before updating  dom0 . The system won't shut down properly if I forget to unmount  /boot . Testing Qubes OS 4.3 rc3 I decided to test the Qubes OS 4.3 rc3 release by performing an in-place upgrade. Unfortunately, the system failed to boot afterward. dracut  Issues After the upgrade, the...
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