Openstack RDO && KVM Hypervisor

Monday, June 8, 2026

FEDORA SERVER 44 BTRFS SETUP and RECOVERY ENGINE (Assisted by Google AI)

In general, instance setup was proposed by Google AI (1-5). My choice was to create four subvolumes followed by "Trick snapper method". (6) I've also suggested to run critical "mv /mnt/btrfs-top/root /mnt/btrfs-top/root_broken" inside the Live F44 (KDE Plasma) instance against crashed instance F44 Server been built on top vda with flat architecture been spread across four btrfs subvolumes "root","home","boot" and ".snapshots"

Original vda layout setup via Anaconda Blivet GUI installation

=====================================================

boris@fedoraSRV0609:~$ lsblk -f

NAME FSTYPE FSVER LABEL UUID FSAVAIL FSUSE% MOUNTPOINTS

zram0 swap 1 zram0 4f083286-72fc-49fc-807d-d4f9a45b447a [SWAP]

vda

├─vda1 vfat FAT32 1C26-CCBE 1014.1M 1% /boot/efi

└─vda2 btrfs fedora-volume 0bdb9d96-5296-4aec-a2a9-e2aceb9f18fd 91.8G 7% /home

/boot

/.snapshots

Originally created /etc/fstab stays untouched due to Trick Snapper Method

boris@fedoraSRV0609:~$ cat /etc/fstab

# /etc/fstab

# Created by anaconda on Mon Jun 8 09:56:27 2026

# Accessible filesystems, by reference, are maintained under '/dev/disk/'.

# See man pages fstab(5), findfs(8), mount(8) and/or blkid(8) for more info.

# After editing this file, run 'systemctl daemon-reload' to update systemd

# units generated from this file.

UUID=0bdb9d96-5296-4aec-a2a9-e2aceb9f18fd / btrfs subvol=root,compress=zstd:1 0 0

UUID=0bdb9d96-5296-4aec-a2a9-e2aceb9f18fd /.snapshots btrfs subvol=snapshots,compress=zstd:1 0 0

UUID=0bdb9d96-5296-4aec-a2a9-e2aceb9f18fd /boot btrfs subvol=boot,compress=zstd:1 0 0

UUID=1C26-CCBE /boot/efi vfat umask=0077,shortname=winnt 0 2

UUID=0bdb9d96-5296-4aec-a2a9-e2aceb9f18fd /home btrfs subvol=home,compress=zstd:1 0 0

$ sudo dnf install btrfs-assistant snapper gawk inotify-tools libdnf5-plugin-actions git make -y

========================

Trick Snapper Method

========================

$ sudo umount /.snapshots

$ sudo rmdir /.snapshots

$ sudo snapper -c root create-config /

$ sudo mkdir /.snapshots

$ sudo mount /.snapshots

1. MANUAL GRUB-BTRFS ENHANCEMENT FROM SOURCE

-----------------------------------------------------------------------------------------

$ git clone https://github.com/Antynea/grub-btrfs.git

$ cd grub-btrfs

$ sudo make install

# Modify /etc/default/grub-btrfs/config with these parameters:

GRUB_BTRFS_GRUB_DIRNAME="/boot/grub2"

GRUB_BTRFS_MKCONFIG="grub2-mkconfig"

GRUB_BTRFS_SCRIPT_CHECK="grub2-script-check"

$ sudo grub2-mkconfig -o /boot/grub2/grub.cfg

$ sudo systemctl daemon-reload

$ sudo systemctl enable --now grub-btrfsd

2. DNF5 TRANSACTION SNAPSHOT AUTOMATION ENGINE

----------------------------------------------------------------------------------------

sudo nano /usr/local/bin/dnf5-snapper-helper

#!/bin/bash

case "$1" in

pre)

/usr/bin/snapper -c root create -t pre -p -d "DNF Transaction" -c number > /tmp/snapper_pre_id

;;

post)

if [ -f /tmp/snapper_pre_id ]; then

PRE_ID=$(cat /tmp/snapper_pre_id)

/usr/bin/snapper -c root create -t post --pre-num "$PRE_ID" -d "DNF Transaction Complete" -c number

rm -f /tmp/snapper_pre_id

;;

esac

$ sudo chmod +x /usr/local/bin/dnf5-snapper-helper

$ sudo nano /etc/dnf/libdnf5-plugins/actions.d/snapper.actions

pre_transaction::::/usr/local/bin/dnf5-snapper-helper pre

post_transaction::::/usr/local/bin/dnf5-snapper-helper post

3. HOUSEKEEPING RETENTION MANAGEMENT

---------------------------------------------------------------------------------------

# Modify /etc/snapper/configs/root with these parameters:

NUMBER_MIN_AGE="1800"

NUMBER_LIMIT="10"

NUMBER_LIMIT_IMPORTANT="10"

TIMELINE_LIMIT_HOURLY="0"

TIMELINE_LIMIT_DAILY="0"

TIMELINE_LIMIT_WEEKLY="0"

TIMELINE_LIMIT_MONTHLY="0"

TIMELINE_LIMIT_YEARLY="0"

4. RUNTIME LIVE CLI RECOVERY (WRITABLE SESSIONS ONLY)

---------------------------------------------------------------------------------------

$ sudo btrfs-assistant --restore <SNAPSHOT_ID>

$ sudo reboot

5. CLEANUP LEFTOVERS AFTER DEPLOYMENT SWAPS

---------------------------------------------------------------------------------------

$ sudo mkdir -p /mnt/btrfs-top

$ sudo mount -o subvolid=5 /dev/vda2 /mnt/btrfs-top

$ sudo btrfs subvolume delete /mnt/btrfs-top/root_dead

$ sudo btrfs subvolume delete /mnt/btrfs-top/root_broken

$ sudo umount /mnt/btrfs-top

$ sudo rmdir /mnt/btrfs-top

Device order during normal runtime

Device order to recover via mounting /dev/vda2 on /mnt/btrfs-top followed by two commands which resulted looping been issued in read-only instance selected via fedora grub sub-menu.

6.BARE-METAL BTRFS LIVE ISO RECOVERY PROTOCOL

----------------------------------------------------------------------------------------

Virtual emulation follows below

Right after crash shutdown instance. Switch order of boot-able devices to F44 ( say KDE Plasma ) Live CD and boot up having both device attached to virt-manager session. Commands below are supposed to run in F44 Live Instance environment see snapshots above. They may be cut from Host and paste into spice console.

As liveuser execute

$ sudo su -

$ mkdir -p /mnt/btrfs-top

$ mount -o subvolid=5 /dev/vda2 /mnt/btrfs-top

$ mv /mnt/btrfs-top/root /mnt/btrfs-top/root_broken

$ btrfs subvolume snapshot /mnt/btrfs-top/snapshots/<RECOVERY_SNAPSHOT_ID>/snapshot /mnt/btrfs-top/root

$ umount /mnt/btrfs-top

Then shutdown Live instance and switch order of boot-able devices back to vda and attempt to boot up from recovered virtual drive

Saturday, May 30, 2026

Google AI has finally decided to setup snapper on Debian forky with btrfs root

The core hack proposed by Google AI Assistant was Navigating the EFI layer. AI targeted the exact 3-line configuration stub (/boot/efi/EFI/debian/grub.cfg) that overrides the Btrfs default subvolume engine on Debian EFI installations. From my side it was integrating a native .path watcher framework precisely because a heavy, compiled inotifywait binary loses its structural handles during a subvolume swap and focus attention on sed substitutions @rootfs with @root_active in grub.cfg files and /etc/fstab.

Virtual disk layout been selected for setup

NAME               FSTYPE      FSVER    LABEL UUID                                   FSAVAIL FSUSE% MOUNTPOINTS
sr0
vda
├─vda1             vfat        FAT32          A381-BF73                                68.6M    12% /boot/efi
├─vda2             btrfs                      8b9cf5c4-b47b-4aba-8146-9494de4446cc     57.6G     9% /.snapshots
│ /
└─vda3             LVM2_member LVM2 001       Ln1ZDW-hEzd-8Ntq-qSh3-v40U-5eYm-krwzXD
├─debianVG-vol01 xfs                        99456d7d-a85e-4f60-9d77-b7ac2511047d     45.1G     3% /var
└─debianVG-vol02 xfs 2c22b8ef-8b21-4304-9396-9c1f2a76493e     27.2G     2% /home

Stage 1

Log into your SSH session, run sudo -i, and execute this block to replicate our successful migration:

# 1. Mount the underlying hard drive partition core
mkdir -p /mnt/btrfs_base
mount -o subvolid=5 /dev/vda2 /mnt/btrfs_base

# 2. Clone the active OS into your production subvolume and build the snapshot container
btrfs subvolume snapshot / /mnt/btrfs_base/@root_active
btrfs subvolume create /mnt/btrfs_base/@snapshots

# 3. Update the storage mapping tables inside the new subvolume clone
nano /mnt/btrfs_base/@root_active/etc/fstab

# <file system> <mount point> <type> <options> <dump> <pass>
# / was on /dev/vda2 during installation
# UUID=8b9cf5c4-b47b-4aba-8146-9494de4446cc / btrfs defaults,subvol=@rootfs 0 0

UUID=8b9cf5c4-b47b-4aba-8146-9494de4446cc / btrfs defaults,subvol=@root_active,compress=zstd,noatime 0 1
UUID=8b9cf5c4-b47b-4aba-8146-9494de4446cc /.snapshots btrfs subvol=@snapshots,compress=zstd,noatime 0 0
# /boot/efi was on /dev/vda1 during installation
UUID=A381-BF73 /boot/efi vfat umask=0077 0 1
/dev/mapper/debianVG-vol02 /home xfs defaults 0 0
/dev/mapper/debianVG-vol01 /var xfs defaults 0 0
/dev/sr0 /media/cdrom0 udf,iso9660 user,noauto 0 0

Stage 2

# 1. Update the main GRUB configuration tracking lines
sed -i 's/@rootfs/@root_active/g' /boot/grub/grub.cfg

# 2. Update the hidden EFI motherboard priority file so it launches the clone
nano /boot/efi/EFI/debian/grub.cfg

boris@debianForky0529:~$ sudo cat /boot/efi/EFI/debian/grub.cfg ( with valid UUID for "/" )
search --no-floppy --fs-uuid --set=root 0123755e-2d03-48e1-9159-5154860a307d
set prefix=($root)/@root_active/boot/grub
configfile $prefix/grub.cfg

(Change the set prefix=($root)/@rootfs... path line to explicitly target /@root_active).

# 3. Rebuild the system kernel modules inside the clone using a clean tool container
# mount --bind /dev /mnt/btrfs_base/@root_active/dev
# mount --bind /proc /mnt/btrfs_base/@root_active/proc
# mount --bind /sys /mnt/btrfs_base/@root_active/sys
# mount /dev/vda1 /mnt/btrfs_base/@root_active/boot/efi
# mount /dev/mapper/debianVG-vol01 /mnt/btrfs_base/@root_active/var  

# chroot /mnt/btrfs_base/@root_active /bin/bash -c "
  update-initramfs -u -k all "

# 1. Step back out to your primary host terminal prompt

exit

# 2. Force the parent GRUB binary to install its EFI modules into the clone's boot folder

$ sudo grub-install --boot-directory=/mnt/btrfs_base/@root_active/boot /dev/vda

# 3. Force the global string replacement on the menu file to direct everything to the clone

$ sudo sed -i 's/@rootfs/@root_active/g' /mnt/btrfs_base/@root_active/boot/grub/grub.cfg

# 4. Clean up mounts and reboot into your new permanent system
$ sudo umount -R /mnt/btrfs_base
$ sudo reboot

Stage 3

Once your VM boots cleanly into @root_active, finalize the deployment:

# 1. Wipe out the old legacy installation footprint permanently
# mkdir -p /mnt/btrfs_base
# mount -o subvolid=5 /dev/vda2 /mnt/btrfs_base
# btrfs subvolume delete /mnt/btrfs_base/@rootfs
# umount /mnt/btrfs_base

# 2. Install Snapper, pull grub-btrfs from source, and run installation paths
# apt install snapper btrfs-progs git make build-essential inotify-tools gawk -y

# 1. Temporarily unmount the default layout path

$ sudo umount /.snapshots

# 2. Force remove the lingering local installer directory block

$ sudo rm -rf /.snapshots

# 3. Force Snapper to create the config profile now that the path is clear

$ sudo snapper -c root create-config /

# 4. Snapper just created a basic folder. Delete it so we can use your real subvolume

$ sudo rmdir /.snapshots

# 5. RE-CREATE THE CORRECT EMPTY MOUNT POINT HOOK

$ sudo mkdir /.snapshots

# 6. MOUNT YOUR PERMANENT SUBVOLUME LAYOUT FROM FSTAB

$ sudo mount -a

# 7. Secure the proper administrative tracking permissions for the engine

$ sudo chmod 750 /.snapshots

$ git clone https://github.com/Antynea/grub-btrfs.git
$ cd grub-btrfs && sudo make install
$ sudo systemctl daemon-reload 
$ sudo systemctl enable --now grub-btrfsd

# 3. Save your rescue script inside /var/local/sbin/snapper-rescue and symlink it
$ sudo chmod +x /var/local/sbin/snapper-rescue
$ sudo ln -s /var/local/sbin/snapper-rescue /usr/local/bin/snapper-rescue

# 4. Rebuild menu paths and lock in your first restore checkpoint
$ sudo update-grub
$ snapper -c root create --description "Baseline Production Setup"

==========================================
Keeping update-grub invoked automatically to maintain "Debian GNU/Linux. grub sub-menu" when system or user issue $ sudo snapper -c root create --description ". . . . "
==========================================
sudo nano /etc/systemd/system/grub-btrfs-watcher.path
[Unit]
Description=Monitor Timeshift Snapshot Directory Changes

[Path]
PathChanged=/.snapshots
Unit=grub-btrfs-watcher.service

[Install]
WantedBy=multi-user.target
=======================================
sudo nano /etc/systemd/system/grub-btrfs-watcher.service
[Unit]
Description=Regenerate GRUB Menu on Snapshot Change

[Service]
Type=oneshot
ExecStart=/usr/sbin/update-grub
======================================
sudo systemctl daemon-reload
sudo systemctl enable --now grub-btrfs-watcher.path

$ sudo reboot

> ssh boris@192.168.0.70
boris@192.168.0.70's password:
Linux debianVM0530 7.0.9+deb14-amd64 #1 SMP PREEMPT_DYNAMIC Debian 7.0.9-1 (2026-05-22) x86_64
The programs included with the Debian GNU/Linux system are free software;
the exact distribution terms for each program are described in the
individual files in /usr/share/doc/*/copyright.

Debian GNU/Linux comes with ABSOLUTELY NO WARRANTY, to the extent
permitted by applicable law.
Last login: Sat May 30 07:59:24 2026 from 192.168.0.81
boris@debianVM0530:~$ sudo snapper -c root list
[sudo] password for boris:

Actually, you are not forced to write script snapper-rescue on your own. Attach Debian Live ISO to virt-manager. Disable load instance from vda and and enable from ISO. You may perform a 3-step terminal override using any Debian Live ISO Instance loaded up

# 1. Mount your base Btrfs drive
$ sudo mount -o subvolid=5 /dev/vda2 /mnt
# 2. Delete the broken active layout
$ sudo btrfs subvolume delete /mnt/@root_active
# 3. Recreate it instantly from your chosen working snapshot (e.g.,Snapshot ID)
$ sudo btrfs subvolume snapshot /mnt/@snapshots/ID/snapshot /mnt/@root_active

When done switch loading device to vda as it was before recovery procedure. Rolling back btrfs "/" volume via Debian Live ISO was tested several times.

To get desired <ID> you are supposed to reboot via Debian Grub-sub-menu and issue $ sudo snapper -c root list and select <ID> which would serve you in Live instance environment to issue $ sudo btrfs subvolume snapshot /mnt/@snapshots/ID/snapshot /mnt/@root_active. Snapper and openssh-server should pre- installed onto Debian Live Instance

Monday, May 25, 2026

Build "Debian GNU/Linux snapshots" grub submenu on forky with timeshift on btrfs root

In particular case several Google's AI Assistant proposals appeared to be questionable and were resolved in development phase. This post is immediate follow up for Setup Timeshift on Debian forky with btrfs root

Setup below would work with following vda virtual disk layout

NAME                FSTYPE      FSVER    LABEL UUID                                   FSAVAIL FSUSE% MOUNTPOINTS
sr0
vda
├─vda1              vfat        FAT32          AD99-8BB9                                68.6M    12% /boot/efi
├─vda2              btrfs                      394a393c-14dd-40d3-801a-6f64bffacaf1 56.6G    10% /home

| /
└─vda3 LVM2_member LVM2 001 3jvYq2-x8VH-5LY6-QYVN-KLiW-KNEJ-K4CpxN
└─debianVGS-vol01 xfs bc73e007-c2dc-47f8-ad9f-390d7da5974d 55.1G 3% /var

what exactly I mean it won't allow partition /boot with ext4 FS . Start configuration of "Debian GNU/Linux snapshots" grub sub-menu :-

$ sudo apt update
$ sudo apt install git make inotify-tools build-essential
$ git clone https://github.com/Antynea/grub-btrfs.git
cd grub-btrfs
# Install the script layout globally
$ sudo make install

$ sudo blkid /dev/vda2 => YOUR_COPIED_UUID_HERE

==================================

UPDATE /etc/grub.d/41_snapshots-btrfs

==================================
$ sudo nano /etc/grub.d/41_snapshots-btrfs
# Root subvolume UUID
# root_uuid_subvolume="$(btrfs subvolume show / 2>/dev/null | \
# awk -F':' '/^\s*UUID/ {gsub(/^[ \t]+/, "", $2); print $2}')"
root_uuid_subvolume="YOUR_COPIED_UUID_HERE"
[ -z "$root_uuid_subvolume" ] && print_error "UUID of the root subvolume is not available"

==================
TUNING BLOCK
==================
$ sudo nano /etc/default/grub-btrfs/config

Add to the bottom

GRUB_BTRFS_SNAPSHOTS_DIRS=("/run/timeshift")
GRUB_BTRFS_SUBVOLUME_DATA_PATH="/"

$ sudo systemctl edit --full grub-btrfsd
[Unit]
Description=Regenerate grub-btrfs.cfg

[Service]
Type=simple
LogLevelMax=notice
# Set the possible paths for `grub-mkconfig`
Environment="PATH=/sbin:/bin:/usr/sbin:/usr/bin"
# Load environment variables from the configuration
EnvironmentFile=/etc/default/grub-btrfs/config
# Start the daemon, usage of it is:
# grub-btrfsd [-h, --help] [-t, --timeshift-auto] [-l, --log-file LOG_FILE] SNAPSHOTS_DIRS
# SNAPSHOTS_DIRS Snapshot directories to watch, without effect when --timeshift-auto
# Optional arguments:
# -t, --timeshift-auto Automatically detect Timeshifts snapshot directory
# -o, --timeshift-old Activate for timeshift versions <22.06
# -l, --log-file Specify a logfile to write to
# -v, --verbose Let the log of the daemon be more verbose
# -s, --syslog Write to syslog
# ExecStart=/usr/bin/grub-btrfsd --syslog /.snapshots

# Directive must be update to support Timeshift
ExecStart=/usr/bin/grub-btrfsd --syslog --timeshift-auto

[Install]
WantedBy=multi-user.target

========================================
# Force systemd to recognize the freshly built paths
$ sudo systemctl daemon-reload
# Enable and start the tracker daemon
$ sudo systemctl enable --now grub-btrfsd
$ sudo systemctl status grub-btrfsd
========================================

As of now
boris@debianVDA2SRV:~$ sudo systemctl status grub-btrfsd
● grub-btrfsd.service - Regenerate grub-btrfs.cfg
Loaded: loaded (/etc/systemd/system/grub-btrfsd.service; enabled; preset: enabled)
Active: active (running) since Sun 2026-05-24 02:49:55 EDT; 6min ago
Invocation: 8132805e3c424d3e856c889243caa91c
Main PID: 870 (bash)
Tasks: 3 (limit: 18558)
Memory: 6.2M (peak: 8.3M)
CPU: 20.783s
CGroup: /system.slice/grub-btrfsd.service
├─ 870 bash /usr/bin/grub-btrfsd --syslog --timeshift-auto
├─ 884 bash /usr/bin/grub-btrfsd --syslog --timeshift-auto
└─4917 sleep 1

May 24 02:56:42 debianVDA2SRV grub-btrfsd[4854]: Watching /run/timeshift for timeshift to start
May 24 02:56:43 debianVDA2SRV grub-btrfsd[4860]: Watching /run/timeshift for timeshift to start

$ sudo update-grub

==========================================
Keeping update-grub invoked automatically
==========================================
sudo nano /etc/systemd/system/grub-btrfs-watcher.path
[Unit]
Description=Monitor Timeshift Snapshot Directory Changes

[Path]
PathChanged=/timeshift-btrfs-snapshots
Unit=grub-btrfs-watcher.service

[Install]
WantedBy=multi-user.target
=======================================
sudo nano /etc/systemd/system/grub-btrfs-watcher.service
[Unit]
Description=Regenerate GRUB Menu on Snapshot Change

[Service]
Type=oneshot
ExecStart=/usr/sbin/update-grub
======================================
sudo systemctl daemon-reload
sudo systemctl enable --now grub-btrfs-watcher.path

Why running both services together works ( commented by Google AI assistent)
The reason this setup operates correctly when both services are enabled simultaneously comes down to how they hand off tasks: Grub-btrfsd acts as the listener. It uses inotifywait to watch /run/timeshift and detect when a snapshot is created or deleted.

Grub-btrfs-watcher.path acts as an administrative bridge.Because it runs as a native systemd tracking primitive, its presence helps elevate permissions when
grub-btrfsd triggers an update event, preventing the background execution from stalling out
over hardcoded XFS /var settings.

Friday, May 22, 2026

Setup Timeshift on Debian forky with btrfs root

By default, the Debian installer names the root subvolume @rootfs. However, Timeshift has a hardcoded requirement looking exclusively for a subvolume named @ (and optionally @home). The core post installation hack was proposed by Google AI Assistant. I've added just one command to second part related with creating @home. The most important step is "The GRUB Edit Route"

Log into your Debian 14 VM normally and rename the subvolumes from underneath the running system.

# Mount the root Btrfs layout to a temporary folder
$ sudo mkdir /tmp/btrfs
$ sudo mount -o subvolid=5 /dev/vda3 /tmp/btrfs (system with /boot on vda2)

# Rename the subvolume
$ sudo mv /tmp/btrfs/@rootfs /tmp/btrfs/@

# Update your fstab immediately so the system knows the new path
$ sudo nano /etc/fstab
# Change "subvol=@rootfs" to "subvol=@" -> Save and exit.

# UPDATE /etc/default/grub
GRUB_CMDLINE_LINUX_DEFAULT="quiet rootflags=subvol=@"

$ sudo update-grub

If your system layout has /var (XFS) and /home (XFS) mounted on separate LVMs belong to VG group say debianVGS . You may reboot in Debian forky an install timeshift via `sudo apt install timeshift` and start Timeshift GUI:

$ sudo timeshift-gtk

If your prefer to keep /home folder under "/" you will be forced to create subvolume @home and mount it as well

# Move the current folder out of the way
$ sudo mv /home /home_backup

# 1. Mount the top-level root pool (ID 5) of your Btrfs drive
$ sudo mkdir /tmp/btrfs_pool
$ sudo mount -o subvolid=5 /dev/vda3 /tmp/btrfs_pool

# 2. Create the exact @home subvolume that Timeshift requires
$ sudo btrfs subvolume create /tmp/btrfs_pool/@home

# 3. Clean up the temporary mount point
$ sudo umount /tmp/btrfs_pool

UPDATE /etc/fstab
UUID=your-vda3-btrfs-uuid /home btrfs defaults,subvol=@home 0 0

# Mount the new subvolume via fstab
$ sudo mkdir /home
$ sudo mount /home

# Move your user data back into the newly mounted subvolume space
$ sudo mv /home_backup/* /home/

# Remove the temporary backup folder
$ sudo rmdir /home_backup

In this case `lsblk -f` would be the following

boris@debianServer:~$ lsblk -f
NAME                FSTYPE      FSVER    LABEL UUID                                   FSAVAIL FSUSE% MOUNTPOINTS
sr0
vda
├─vda1              vfat        FAT32          58CD-C1FE                                68.6M    12% /boot/efi
├─vda2              ext4        1.0            119959dd-f1b2-493c-9964-58eeb7e318e5      1.6G     6% /boot
├─vda3              btrfs                      590ce0cb-91da-4cd1-bb2c-1964e87765bb     65.2G     8% /home
│ /
└─vda4              LVM2_member LVM2 001       uZtjyt-T4dM-2nf5-NW4n-wBAL-0iOf-3lir1Y
└─debianVGT-vol01 xfs                        db513736-ebef-436a-871a-8a3d7b556900     45.1G     3% /var

In case when /var (xfs) and /home (xfs) are mounted on separate LVMs creating subvolume @home is not your concern only @rootfs should be changed to @ ( code above first snapshot )

boris@debian14VM:~$ lsblk -f
NAME               FSTYPE      FSVER    LABEL UUID                                   FSAVAIL FSUSE% MOUNTPOINTS
sr0
vda
├─vda1             vfat        FAT32          3577-8495                                68.6M    12% /boot/efi
├─vda2             ext4        1.0            d3dd2332-1f6f-4c40-9273-c2c5d6b9f41a      1.6G     6% /boot
├─vda3             btrfs                      2658de53-7273-4133-9a18-a140bf872a9b     46.2G    12% /
└─vda4             LVM2_member LVM2 001       TDj8QE-QtAa-Kfxl-WWxB-aXVE-yVLs-UARNr4
├─DebianVG-VOL01 xfs                        df364b9e-281a-4edb-b2d0-0be1f6b909f8     49.9G    11% /var
└─DebianVG-VOL02 xfs                        aacb7d6e-dd1a-4ddf-8177-ccdc0017618b     25.6G     8% /home

For disk layout without /boot (ext4) folder hackery code would be a bit more complicated

$ sudo mkdir /tmp/btrfs_raw
$ sudo mount -o subvolid=5 /dev/vda2 /tmp/btrfs_raw

# 2. Rename subvolume
$ sudo mv /tmp/btrfs_raw/@rootfs /tmp/btrfs_raw/@

# 3. Create temporary safety symlink
$ sudo ln -s @ /tmp/btrfs_raw/@rootfs

# 4. Update fstab
$ sudo sed -i 's/subvol=@rootfs/subvol=@/g' /etc/fstab

# 5. Permanently lock the boot parameter
$ sudo sed -i 's/GRUB_CMDLINE_LINUX_DEFAULT="/GRUB_CMDLINE_LINUX_DEFAULT="rootflags=subvol=@ /' /etc/default/grub

# 6. Update GRUB and reboot
$ sudo update-grub
$ sudo umount /tmp/btrfs_raw
$ sudo reboot

In the last case "/" btrfs folder would be mounted on /dev/vda2 rather then /dev/vda3

Thursday, May 7, 2026

Speed-Optimized Python 3.14t on Debian Forky: A Clang-19 Build Guide (Assisted by Google AI)

UPDATE as of 05/19/26

Same build would work for Python-3.14.5.tar.xz on Debian Trixie 13.5

END UPDATE

Building multi-threaded Python 3.14+ from source on Debian Forky using Clang 19.1 enables high-performance, free-threaded execution (no GIL). Using clang-19 with optimized flags (-O3, -flto) and linking against libatomic1 (Debian/Ubuntu) ensures maximum performance and thread safety, crucial for taking advantage of modern multi-core architectures.

Build Configuration Highlights:
Compiler: Clang 19.1 (optimized for Debian Forky).
Interpreter Logic: Enabled "--with-tail-call-interp" for ~3-5% baseline improvement. Threading: --disable-gil for multi-core parallelism (3.14t). Optimization Pipeline: Full PGO + LTO cycle, which is essential for the tail-call interpreter to reach peak performance.

Setup Packages for build :

Step 1

$ sudo apt update && sudo apt install -y make build-essential libssl-dev zlib1g-dev libbz2-dev libreadline-dev libsqlite3-dev wget curl llvm clang-19 libncurses-dev xz-utils tk-dev libxml2-dev libxmlsec1-dev libffi-dev liblzma-dev git gcc libclang-19-dev libdb5.3-dev libgdbm-dev

Step 2

$ sudo apt update && sudo apt install -y binutils libc6-dev libstdc++-14-dev

Step 3

Because Forky is a testing branch, package dependencies are sometimes in flux. For a stable build environment, you should ensure clang-19 is the active version by setting up alternatives if you plan to build frequently

$ sudo update-alternatives --install /usr/bin/clang clang /usr/bin/clang-19 100

Verify compiler setup

$ clang-19 --version

$ vi test.c

#include <stdio.h>

int main() { printf("Works\n"); return 0; }

:wq

$ clang-19 test.c -o test && ./test

Works

=================================================
Now configure && build from source with clang-19 pre-installed
=================================================
$ tar -xf Python-3.14.4.tar.xz
$ cd Python-3.14.4
$ CC=clang-19 ./configure --enable-optimizations --with-lto --disable-gil --with-tail-call-interp
$ make -j10
$ sudo make altinstall

Configure working directory and install required packages into Python virtual environment :

$ mkdir WORKMTH

$ cd WORKMTH
$ python3.14t -m venv .env
$ source .env/bin/activate
$ pip install aqtinstall
$ pip install --upgrade pip
$ pip install numpy matplotlib cxroots

$ pip install seaborn

Several code samples

$ cat meromorphPlotting01.py
import numpy as np

import matplotlib.pyplot as plt
from scipy.optimize import fsolve
from concurrent.futures import ThreadPoolExecutor
import csv

# 1. Function Definitions
def f_num(z):
    # Multiple root at origin (z^9 factor + sinh term also zero at 0)
    return z**16 + 7*z**11 + 6*z**9*np.sinh(np.pi*z)

def f_den(z):
    # Multiple root at origin (z^2)
    return z**12 + 3*z**5 + z**2

def f(z):
    return f_num(z) / f_den(z)

# 2. Multiplicity and Root Hunting
def get_multiplicity(z0, is_numerator):
    """Calculates order of root at z0 via local winding integral."""
    eps = 1e-5
    theta = np.linspace(0, 2*np.pi, 1000)
    z_circle = z0 + eps * np.exp(1j * theta)
    vals = f_num(z_circle) if is_numerator else f_den(z_circle)
    m = int(round(np.sum(np.diff(np.unwrap(np.angle(vals)))) / (2 * np.pi)))
    return max(m, 1)

def find_root_worker(is_numerator, seed):
    def func_to_solve(v):
        z = complex(v[0], v[1])
        val = f_num(z) if is_numerator else f_den(z)
        return [val.real, val.imag]
    sol, info, ier, msg = fsolve(func_to_solve, seed, full_output=True, xtol=1e-10)
    return complex(sol[0], sol[1]) if ier == 1 else None

def get_unique_roots_parallel(is_numerator, n_attempts=500):
    seeds = [np.random.uniform(-2.5, 2.5, 2) for _ in range(n_attempts)]
    with ThreadPoolExecutor() as executor:
        results = list(executor.map(lambda s: find_root_worker(is_numerator, s), seeds))
    
    # Manual inclusion of origin to ensure it's not missed by solver
    found_roots = [r for r in results if r is not None]
    found_roots.append(0.0 + 0.0j)
    
    unique_data = []
    for r in found_roots:
        if not any(np.isclose(r, u[0], atol=1e-4) for u in unique_data):
            m = get_multiplicity(r, is_numerator)
            unique_data.append((r, m))
    
    unique_data.sort(key=lambda x: (round(x[0].real, 4), round(x[0].imag, 4)))
    all_roots = [r for r, m in unique_data for _ in range(m)]
    return all_roots, unique_data

# 3. Execution and Processing
R_contour = 2.0
zeros_all, zeros_unique = get_unique_roots_parallel(True)
poles_all, poles_unique = get_unique_roots_parallel(False)

# Numerical Winding Calculation
phi_vals = np.linspace(0, 2*np.pi, 300000)
def get_p(p): return np.angle(f(R_contour * np.exp(1j * p)))
with ThreadPoolExecutor() as executor:
    phases = np.concatenate(list(executor.map(get_p, np.array_split(phi_vals, 8))))
winding_num = int(round((np.unwrap(phases)[-1] - np.unwrap(phases)[0]) / (2 * np.pi)))

# 4. Final Printing
print(f"{'TYPE':<8} | {'REAL':<10} | {'IMAG':<10} | {'MULTIPLICITY':<12} | {'MAGNITUDE'}")
print("-" * 65)
for r, m in zeros_unique:
    print(f"{'ZERO':<8} | {r.real:10.5f} | {r.imag:10.5f} | {m:<12} | {np.abs(r):.4f}")
for p, m in poles_unique:
    print(f"{'POLE':<8} | {p.real:10.5f} | {p.imag:10.5f} | {m:<12} | {np.abs(p):.4f}")

print(f"\n--- SUMMARY ---")
print(f"Total Z (with mult): {len(zeros_all)}")
print(f"Total P (with mult): {len(poles_all)}")
print(f"Winding (Z-P): {len(zeros_all)-len(poles_all)} | Integral: {winding_num}")

# 5. Phase Portrait Plotting
plt.figure(figsize=(11, 9))
res = 500
lim = 2.5
x, y = np.linspace(-lim, lim, res), np.linspace(-lim, lim, res)
X, Y = np.meshgrid(x, y)
# Domain coloring background
plt.pcolormesh(X, Y, np.angle(f(X + 1j*Y)), cmap='hsv', alpha=0.4, shading='gouraud')

# Overlay Roots - markers grow with multiplicity
for r, m in zeros_unique:
    plt.scatter(r.real, r.imag, s=50*m, edgecolors='blue', facecolors='none', lw=1.5, label='Zeros' if r == zeros_unique[0][0] else "")
for p, m in poles_unique:
    plt.scatter(p.real, p.imag, s=50*m, marker='*', color='black', label='Poles' if p == poles_unique[0][0] else "")

# Contour and Title
plt.plot(R_contour*np.cos(phi_vals), R_contour*np.sin(phi_vals), 'k--', label=f'Contour R={R_contour}')
plt.title(fr"$\Delta \arg f(z) = 2\pi(Z - P)$ | Winding = {winding_num}")
plt.axis('equal'); plt.grid(True, alpha=0.2); plt.legend(loc='upper right')
plt.show()

 
$ cat plotMulti3DSeaborn01.py
import numpy as np
import matplotlib.pyplot as plt
import seaborn as sns
from matplotlib.tri import Triangulation
from concurrent.futures import ProcessPoolExecutor
# --- Parallel Worker Functions ---

def calc_paraboloid():
   X, Y = np.meshgrid(np.linspace(-5, 5, 100), np.linspace(-5, 5, 100))
   Z = X**2 + Y**2
   # Return (plot_type, data, palette, title)
   return ('surface', (X, Y, Z), 'rocket', 'Paraboloid')

def calc_sine_tri():
   X, Y = np.meshgrid(np.linspace(-5, 5, 50), np.linspace(-5, 5, 50))
   Z = np.sin(np.sqrt(X**2 + Y**2))
   triang = Triangulation(X.flatten(), Y.flatten())
   return ('trisurf', (triang, Z.flatten()), 'viridis', 'Sine Triangulation')

def calc_mobius():
   theta, w = np.meshgrid(np.linspace(0, 2*np.pi, 100), np.linspace(-0.5, 0.5, 10))
   r = 1 + w * np.cos(theta / 2)
   x, y, z = r * np.cos(theta), r * np.sin(theta), w * np.sin(theta / 2)
   return ('surface', (x, y, z), 'mako', 'Möbius Strip')

if __name__ == "__main__":
   # Apply Seaborn dashboard styling
   sns.set_theme(style="white")   
  # 1. Execute calculations in parallel
  with ProcessPoolExecutor() as executor:
       futures = [
           executor.submit(calc_paraboloid),
           executor.submit(calc_sine_tri),
           executor.submit(calc_mobius)
       ]
       results = [f.result() for f in futures]

   # 2. Main Thread Rendering: Combined Dashboard

fig = plt.figure(figsize=(18, 6))
for i, (plot_type, data, palette, title) in enumerate(results, 1):
       ax = fig.add_subplot(1, 3, i, projection='3d')
       # Pull the Seaborn color palette
       cmap = sns.color_palette(palette, as_cmap=True)
       if plot_type == 'surface':
           ax.plot_surface(*data, cmap=cmap, edgecolor='none', alpha=0.9)
       else:
           ax.plot_trisurf(*data, cmap=cmap, edgecolor='none')

ax.set_title(title, fontsize=14, fontweight='bold', pad=20)
ax.xaxis.set_pane_color((1.0, 1.0, 1.0, 0.0))
plt.tight_layout()
plt.show()

$ cat complexThreaded09.py
import os
import numpy as np
import matplotlib.pyplot as plt
from cxroots import Circle
from concurrent.futures import ThreadPoolExecutor

# Silence Qt warnings
os.environ["QT_LOGGING_RULES"] = "*.debug=false;qt.qpa.fonts.warning=false"

def count_zeros_task(f, df, contour_points):
  """Calculates zeros via the Argument Principle."""
  fz, dfz = f(contour_points), df(contour_points)
  integrand = dfz / fz
  dz = np.diff(contour_points, append=contour_points[0])
  integral = np.sum(integrand * dz)
  return int(np.round((integral / (2j * np.pi)).real))

def find_roots_task(contour, f, df):
  """Calculates specific root locations using cxroots."""
  return contour.roots(f, df)

# 1. Setup Data
f = lambda z: 4*z**5 + 4*z**3 - 4*z + 9
df = lambda z: 20*z**4 + 12*z**2 - 4
t = np.linspace(0, 2 * np.pi, 1000)
circle_pts = 4 * np.exp(1j * t)
C = Circle(0, 4)

print("Starting concurrent calculations...")

# 2. Parallel Execution
with ThreadPoolExecutor() as executor:
  # Submit both tasks to run simultaneously
  future_count = executor.submit(count_zeros_task, f, df, circle_pts)
  future_roots = executor.submit(find_roots_task, C, f, df)

  # Retrieve results (this waits for each to finish)
  zero_count = future_count.result()
  roots_result = future_roots.result()

# 3. Output and Visualization
print(f"\nVerification (Argument Principle): {zero_count} zeros found.")
print(f"Detailed Root Analysis:\n{roots_result}")

# Plotting must happen on the main thread
roots_result.show()
plt.show()