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. 

 

 

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

 

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

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()

Bring CachyOS Cosmic 1.0.11 DE along with kernel 7.0.1 to Arch Linux (VENV)

 Following below is procedure which allows to install on Arch Linux CachyOS v3 repositories along with pacman fork belongs to CachyOS. Due to rolling style of both distros sequence of steps would be slightly different the one that was proposed in earlier posts described the same procedure. Issues during migration  CachyOS's ( as of 04/26/26  ) Cosmic to Arch  may also depends on your physical location. You may obtain different repos lists generated by cachyos-rate-mirrors due to WAN routing  might be updated since your the most recent attempt to succeed with procedure mentioned in the header. Due to stabilizing of Cosmic DE 1.0.10/11 I believe that getting Cosmic DE ported to Arch Linux from CachyOS is worth efforts undertaken below .

 $ cat SignCachyos.sh
sudo rm -rf /etc/pacman.d/gnupg/
sudo pacman-key --init
sudo pacman-key --populate
sudo pacman-key --recv-keys F3B607488DB35A47 --keyserver keyserver.ubuntu.com
sudo pacman-key --lsign-key F3B607488DB35A47
sudo rm -R /var/lib/pacman/sync

$ ./SignCachyos.sh

Next Step

 $ curl https://mirror.cachyos.org/cachyos-repo.tar.xz -o cachyos-repo.tar.xz
$ tar xvf cachyos-repo.tar.xz && cd cachyos-repo

Following  step in particular installs pacman's fork belongs to CachyOS
$ sudo ./cachyos-repo.sh
$ cd
Scp binary cachyos-rate-mirrors  from native CachyOS box to target one.

$ vim .bashrc
Add at bottom of .bashrc function u() :-
u() {
    # Check if pacman is locked by another process
    if [ -f /var/lib/pacman/db.lck ]; then
        echo "Pacman is locked. Attempting to remove stale lock file..."
        sudo rm /var/lib/pacman/db.lck
    fi
    # 1. Refresh mirrors and update system via yay
    sudo cachyos-rate-mirrors && yay --noconfirm
    # 2. Clear pacman cache (keep only the last 3 versions of each package)
    # Using 'yes' to automate the prompt safely
    yes | sudo paccache -rk3
    # 3. Remove orphaned packages (unused dependencies)
    # The 'if' check prevents errors if no orphans are found
    ORPHANS=$(pacman -Qtdq)
    if [ -n "$ORPHANS" ]; then
        sudo pacman -Rns $ORPHANS --noconfirm
    else
        echo "No orphaned packages to remove."
    fi
}
:wq

In my case following setup gives the most stable results:

$ source ~/.bashrc ;  $ rate-mirrors cachyos && yay
$ u  # which is supposed to invoke cachyos-rate-mirrors

and allows to avoid running procedure (***). See also Google AI comment on this case right below

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

Why this sequence works

   1. Avoids "Dirty" Mirrors: The "invalid signature" error often occurs when a mirror is in the middle of a sync and serves an updated database but older packages (or vice versa), causing a PGP mismatch. rate-mirrors  finds the most up-to-date and fastest mirrors immediately, effectively "skipping" the problematic server.
    Independent Ranking: rate-mirrors cachyos is a direct tool that fetches fresh mirror data without relying
    on your potentially broken local configuration.
    Preparing for the Script: cachyos-rate-mirrors is actually a wrapper script that performs extra steps like
    updating the keyring. By running yay (which triggers a sync) right after a manual mirror rank, you ensure
    your package database is synchronized with a healthy server before the script attempts its automated updates.
    Keyring Refresh: The underlying issue is often a GPG keyring mismatch or an expired key.
    The subsequent sudo cachyos-rate-mirrors then has a higher success rate because it connects to the validated
    "good" mirrors you just discovered, allowing it to correctly pull the new cachyos-keyring.

2. Your workaround solves the source problem rather than the local key problem:
    Switching to "Fresh" Tier 1 Mirrors: rate-mirrors cachyos forces your system to drop any mirrors
    currently in the middle of a sync and jump to a Tier 1 mirror that has the complete set of extra-v3 signatures ready. The Pre-Sync (yay): Running yay (which performs a pacman -Sy) immediately after ranking creates a verified local cache of the repo metadata.
    The Wrapper Completion: By the time sudo cachyos-rate-mirrors runs, the "path is cleared." The script doesn't  have to fight with a mismatched extra-v3 signature from a slow mirror, allowing it to finish the configuration of your Haswell-optimized environment 

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

#!/bin/bash (***)
# A script to fix PGP signature errors on Arch/CachyOS
echo "--- Syncing system clock (Required for GPG) ---"
sudo timedatectl set-ntp true
echo "--- Clearing old keyring data ---"
sudo rm -rf /etc/pacman.d/gnupg
echo "--- Initializing new keyring ---"
sudo pacman-key --init
echo "--- Populating Arch and CachyOS keys ---"
sudo pacman-key --populate archlinux cachyos
echo "--- Force-updating keyring packages ---"
sudo pacman -Sy archlinux-keyring cachyos-keyring --noconfirm
echo "--- Success! You can now run 'sudo pacman -Syu' ---"  

 Right after successful u() completion install Cachyos kernel and reboot Arch Linux VM into CachyOS kernel

$ sudo pacman -S linux-cachyos linux-cachyos-headers

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

$ sudo reboot

 On Arch VM rebooted into Cachyos kernel

$ u 

Attempt to run `sudo pacman -Syyu` is supposed to perform final repositories synchronization .

❯ ssh boris@192.168.0.150
boris@192.168.0.150's password:  
[boris@ArchCosmic290426 ~]$ fastfetch
                 -`                     boris@ArchCosmic290426
                  Host: KVM/QEMU Standard PC (Q35 + ICH9, 2009) (pc-q35-11.0)
             `+oooooo:                  Kernel: Linux 7.0.1-1-cachyos
             -+oooooo+:                 Uptime: 38 mins
           `/:-:++oooo+:                Packages: 650 (pacman)
          `/++++/+++++++:               Shell: bash 5.3.9
         `/++++++++++++++:              Display (QEMU Monitor): 1920x1080 in 15", 60 Hz
        `/+++ooooooooooooo/`            Terminal: /dev/pts/1
       ./ooosssso++osssssso+`           CPU: 10 x Intel(R) Xeon(R) E5-2690 v3 (10) @ 2.59 GHz
      .oossssso-````/ossssss+`          GPU: RedHat Virtio 1.0 GPU
     -osssssso.      :ssssssso.         Memory: 1.52 GiB / 15.24 GiB (10%)
    :osssssss/        osssso+++.        Swap: 0 B / 4.00 GiB (0%)
   /ossssssss/        +ssssooo/-        Disk (/): 8.88 GiB / 74.00 GiB (12%) - btrfs
 `/ossssso+/:-        -:/+osssso+-      Local IP (enp1s0): 192.168.0.150/24
`+sso+:-`                 `.-/+oso:     Locale: en_US.UTF-8
`++:.                           `-/+/
.`                                 `/                             
                                                                 
[boris@ArchCosmic290426 ~]$  sudo pacman -Syyu
[sudo] password for boris:  
:: Synchronizing package databases...
cachyos-v3                                                 124.6 KiB   197 KiB/s 00:01 [##################################################] 100%
cachyos-core-v3                                            111.5 KiB   149 KiB/s 00:01 [##################################################] 100%
cachyos-extra-v3                                             4.1 MiB  1645 KiB/s 00:03 [##################################################] 100%
cachyos                                                    524.2 KiB   304 KiB/s 00:02 [##################################################] 100%
core                                                       124.4 KiB   300 KiB/s 00:00 [##################################################] 100%
extra                                                        8.2 MiB  5.92 MiB/s 00:01 [##################################################] 100%
:: Starting full system upgrade...
there is nothing to do
[boris@ArchCosmic290426 ~]$ pacman -Qi pacman
Installed From  : cachyos
Name            : pacman
Version         : 7.1.0.r9.g54d9411-2
Description     : A library-based package manager with dependency support. CachyOS fork.
Architecture    : x86_64
URL             : https://www.archlinux.org/pacman/
Licenses        : GPL-2.0-or-later
Groups          : None
Provides        : libalpm.so=16-64
Depends On      : bash  coreutils  curl  libcurl.so=4-64  gawk  gettext  glibc  gnupg  gpgme  libgpgme.so=45-64  grep  libarchive
                 libarchive.so=13-64  openssl  libcrypto.so=3-64  pacman-mirrorlist  systemd  libmakepkg-dropins
Optional Deps   : base-devel: required to use makepkg [installed]
                 perl-locale-gettext: translation support in makepkg-template
Required By     : appstream-glib  archlinux-keyring  base  base-devel  chwd  libpamac-aur  pacman-contrib  paru  yay
Optional For    : None
Conflicts With  : None
Replaces        : None
Installed Size  : 10.27 MiB
Packager        : CachyOS <admin@cachyos.org>
Build Date      : Sun 18 Jan 2026 01:58:00 PM MSK
Install Date    : Tue 28 Apr 2026 10:21:41 AM MSK
Install Reason  : Installed as a dependency for another package
Install Script  : No
Validated By    : Signature

At this point you may also perform a complete upgrade system to CachyOS

$ sudo pacman -S ananicy-cpp
$ sudo pacman -S cachyos-kernel-manager
$ pacman -Qqn | sudo pacman -S -

Verification step

[boris@ArchCosmic290426 ~]$  pacman -Qs cachyos
local/cachyos-kernel-manager 1.17.0-1 (cachyos)
   Simple kernel manager
local/cachyos-keyring 20240331-1 (cachyos)
   CachyOS keyring
local/cachyos-mirrorlist 27-1 (cachyos)
   CachyOS repository mirrorlist
local/cachyos-v3-mirrorlist 27-1 (cachyos)
   CachyOS repository mirrorlist
local/cachyos-v4-mirrorlist 27-1 (cachyos)
   CachyOS repository mirrorlist
local/chwd 1.21.0-1 (cachyos)
   CachyOS Hardware Detection Tool
local/linux-cachyos 7.0.1-1
   The Linux EEVDF + LTO + AutoFDO + Propeller Cachy Sauce Kernel by CachyOS with other patches and improvements. kernel and modules
local/linux-cachyos-headers 7.0.1-1
   Headers and scripts for building modules for the Linux EEVDF + LTO + AutoFDO + Propeller Cachy Sauce Kernel by CachyOS with other patches and
   improvements. kernel
local/pacman 7.1.0.r9.g54d9411-2
   A library-based package manager with dependency support. CachyOS fork.
local/scx-manager 1.15.10-2 (cachyos)
   Simple GUI for managing sched-ext schedulers via scx_loader

 

 
[boris@ArchCosmic290426 ~]$ pacman -Ss cosmic-*
cachyos-extra-v3/cosmic-app-library 1:1.0.11-1.1 (cosmic) [installed]
   Cosmic App Library
cachyos-extra-v3/cosmic-applets 1:1.0.11-1.1 (cosmic) [installed]
   Applets for COSMIC Panel
cachyos-extra-v3/cosmic-bg 1:1.0.11-1.1 (cosmic) [installed]
   COSMIC session service which applies backgrounds to displays
cachyos-extra-v3/cosmic-comp 1:1.0.11-1.1 (cosmic) [installed]
   Compositor for the COSMIC desktop environment
cachyos-extra-v3/cosmic-files 1:1.0.11-1.1 (cosmic) [installed]
   File manager for the COSMIC desktop environment
cachyos-extra-v3/cosmic-greeter 1:1.0.11-1.1 (cosmic) [installed]
   COSMIC greeter for greetd
cachyos-extra-v3/cosmic-idle 1:1.0.11-1.1 (cosmic) [installed]
   Cosmic idle daemon
cachyos-extra-v3/cosmic-initial-setup 1:1.0.11-1.1 (cosmic) [installed]
   COSMIC Initial Setup
cachyos-extra-v3/cosmic-launcher 1:1.0.11-1.1 (cosmic) [installed]
   Layer Shell frontend for Pop Launcher
cachyos-extra-v3/cosmic-notifications 1:1.0.11-1.1 (cosmic) [installed]
   Layer Shell notifications daemon which integrates with COSMIC
cachyos-extra-v3/cosmic-osd 1:1.0.11-1.1 (cosmic) [installed]
   COSMIC On-Screen Display
cachyos-extra-v3/cosmic-panel 1:1.0.11-1.1 (cosmic) [installed]
   XDG Shell Wrapper Panel for Cosmic
cachyos-extra-v3/cosmic-player 1:1.0.11-1.1 (cosmic) [installed]
   WIP COSMIC media player
cachyos-extra-v3/cosmic-randr 1:1.0.11-1.1 (cosmic) [installed]
   Library and utility for displaying and configuring Wayland outputs
cachyos-extra-v3/cosmic-screenshot 1:1.0.11-1.1 (cosmic) [installed]
   Utility for capturing screenshots via XDG Desktop Portal
cachyos-extra-v3/cosmic-session 1:1.0.11-1.1 (cosmic) [installed]
   Session manager for the COSMIC desktop environment
cachyos-extra-v3/cosmic-settings 1:1.0.11-1.1 (cosmic) [installed]
   The settings application for the COSMIC desktop environment
cachyos-extra-v3/cosmic-settings-daemon 1:1.0.11-1.1 (cosmic) [installed]
   Cosmic settings daemon
cachyos-extra-v3/cosmic-store 1:1.0.11-1.1 (cosmic) [installed]
   Cosmic App Store
cachyos-extra-v3/cosmic-terminal 1:1.0.11-1.1 (cosmic) [installed]
   Cosmic Terminal Emulator
cachyos-extra-v3/cosmic-text-editor 1:1.0.11-1.1 (cosmic) [installed]
   Text editor for the COSMIC desktop
cachyos-extra-v3/cosmic-workspaces 2:1.0.11-1.1 (cosmic) [installed]
   Cosmic workspaces
cachyos-extra-v3/xdg-desktop-portal-cosmic 1:1.0.11-1.1 (cosmic) [installed]
   A backend implementation for xdg-desktop-portal for the COSMIC desktop environment
cachyos/cosmic-app-library-git 1.0.0.alpha.7.r14.g8b520ec-1
   An application launcher for the COSMIC desktop
cachyos/cosmic-applets-git 1.0.11.r2.gae3f722-1
   Applets for COSMIC Panel
cachyos/cosmic-applibrary-git 1.0.0.alpha.3.r1.g676656d-1
   An application launcher for the COSMIC desktop
cachyos/cosmic-bg-git 1.0.11.r0.g06970d5-1
   COSMIC session service which applies backgrounds to displays.
cachyos/cosmic-comp-git 1.0.11.r2.gce5ac89-1
   Compositor for the COSMIC desktop environment
cachyos/cosmic-edit-git 1.0.11.r0.g5f96f61-1
   Text editor for the COSMIC desktop
cachyos/cosmic-files-git 1.0.11.r0.gb3af8bf-1
   File manager for the COSMIC desktop environment
cachyos/cosmic-greeter-git 1.0.11.r0.g619910c-1
   libcosmic greeter for greetd, which can be run inside cosmic-comp
cachyos/cosmic-icons-git 1.0.0.beta.1.r0.g70b0758-1
   System76 Cosmic icon theme
cachyos/cosmic-idle-git 1.0.0.alpha.7.r0.g267bb83-1
   Cosmic idle daemon
cachyos/cosmic-launcher-git 1.0.11.r0.g2bdac13-1
   Layer Shell frontend for Pop Launcher.
cachyos/cosmic-notifications-git 1.0.11.r0.gdbd0658-1
   Layer Shell notifications daemon which integrates with COSMIC.
cachyos/cosmic-osd-git 1.0.11.r1.gcbc1e9c-1
   COSMIC On-Screen Display
cachyos/cosmic-panel-git 1.0.11.r0.gd518c7d-1
   XDG Shell Wrapper Panel for COSMIC
cachyos/cosmic-randr-git 1.0.0.beta.1.r0.gbce9cdf-1
   Library and utility for displaying and configuring Wayland outputs
cachyos/cosmic-screenshot-git 1.0.10.r0.g2a8f809-1
   Utility for capturing screenshots via XDG Desktop Portal
cachyos/cosmic-session-git 1.0.0.beta.5.r0.g472db42-1
   Session manager for the COSMIC desktop environment
cachyos/cosmic-settings-daemon-git 1.0.10.r0.g716da6d-1
   Cosmic settings daemon
cachyos/cosmic-settings-git 1.0.11.r5.gfa085f9-1
   The settings application for the COSMIC desktop environment.
cachyos/cosmic-term-git 1.0.10.r2.gc930689-1
   COSMIC Terminal Emulator
cachyos/cosmic-wallpapers-git 1.0.8.r0.g3c59953-1
   Wallpapers for the COSMIC Desktop Environment
cachyos/cosmic-workspaces-git 1.0.10.r0.g4e9c902-1
   Cosmic workspaces
cachyos/xdg-desktop-portal-cosmic-git 1.0.11.r0.g0917743-1
   A backend implementation for xdg-desktop-portal for the COSMIC desktop environment
extra/cosmic-app-library 1:1.0.11-1 (cosmic) [installed: 1:1.0.11-1.1]
   Cosmic App Library
extra/cosmic-applets 1:1.0.11-1 (cosmic) [installed: 1:1.0.11-1.1]
   Applets for COSMIC Panel
extra/cosmic-bg 1:1.0.11-1 (cosmic) [installed: 1:1.0.11-1.1]
   COSMIC session service which applies backgrounds to displays
extra/cosmic-comp 1:1.0.11-1 (cosmic) [installed: 1:1.0.11-1.1]
   Compositor for the COSMIC desktop environment
extra/cosmic-files 1:1.0.11-1 (cosmic) [installed: 1:1.0.11-1.1]
   File manager for the COSMIC desktop environment
extra/cosmic-greeter 1:1.0.11-1 (cosmic) [installed: 1:1.0.11-1.1]
   COSMIC greeter for greetd
extra/cosmic-icon-theme 1:1.0.11-1 [installed]
   Cosmic icon theme
extra/cosmic-idle 1:1.0.11-1 (cosmic) [installed: 1:1.0.11-1.1]
   Cosmic idle daemon
extra/cosmic-initial-setup 1:1.0.11-1 (cosmic) [installed: 1:1.0.11-1.1]
   COSMIC Initial Setup
extra/cosmic-launcher 1:1.0.11-1 (cosmic) [installed: 1:1.0.11-1.1]
   Layer Shell frontend for Pop Launcher
extra/cosmic-notifications 1:1.0.11-1 (cosmic) [installed: 1:1.0.11-1.1]
   Layer Shell notifications daemon which integrates with COSMIC
extra/cosmic-osd 1:1.0.11-1 (cosmic) [installed: 1:1.0.11-1.1]
   COSMIC On-Screen Display
extra/cosmic-panel 1:1.0.11-1 (cosmic) [installed: 1:1.0.11-1.1]
   XDG Shell Wrapper Panel for Cosmic
extra/cosmic-player 1:1.0.11-1 (cosmic) [installed: 1:1.0.11-1.1]
   WIP COSMIC media player
extra/cosmic-randr 1:1.0.11-1 (cosmic) [installed: 1:1.0.11-1.1]
   Library and utility for displaying and configuring Wayland outputs
extra/cosmic-screenshot 1:1.0.11-1 (cosmic) [installed: 1:1.0.11-1.1]
   Utility for capturing screenshots via XDG Desktop Portal
extra/cosmic-session 1:1.0.11-1 (cosmic) [installed: 1:1.0.11-1.1]
   Session manager for the COSMIC desktop environment
extra/cosmic-settings 1:1.0.11-1 (cosmic) [installed: 1:1.0.11-1.1]
   The settings application for the COSMIC desktop environment
extra/cosmic-settings-daemon 1:1.0.11-1 (cosmic) [installed: 1:1.0.11-1.1]
   Cosmic settings daemon
extra/cosmic-store 1:1.0.11-1 (cosmic) [installed: 1:1.0.11-1.1]
   Cosmic App Store
extra/cosmic-terminal 1:1.0.11-1 (cosmic) [installed: 1:1.0.11-1.1]
   Cosmic Terminal Emulator
extra/cosmic-text-editor 1:1.0.11-1 (cosmic) [installed: 1:1.0.11-1.1]
   Text editor for the COSMIC desktop
extra/cosmic-wallpapers 2:1.0.11-1 (cosmic) [installed]
   Wallpapers for the COSMIC Desktop Environment
extra/cosmic-workspaces 2:1.0.11-1 (cosmic) [installed: 2:1.0.11-1.1]
   Cosmic workspaces
extra/xdg-desktop-portal-cosmic 1:1.0.11-1 (cosmic) [installed: 1:1.0.11-1.1]
   A backend implementation for xdg-desktop-portal for the COSMIC desktop environment