Convert running Ubuntu system to Arch Linux

ramroot.sh

#!/bin/bash

# Install prereqs - Ubuntu
apt-get update && apt-get -y install \
  qemu-utils

# Stop services 
df -TH > mounted_fs
systemctl list-units \
  --type=service \
  --state=running \
  --no-pager \
  --no-legend \
  | awk '!/ssh/ {print $1}' \
  | xargs systemctl stop

# Stop DNS from breaking
echo "nameserver 8.8.8.8" > /etc/resolv.conf

# Copy old root to tmpfs
umount -a
mkdir /tmp/tmproot
mount none /tmp/tmproot -t tmpfs
mkdir /tmp/tmproot/{proc,sys,usr,var,run,dev,tmp,home,oldroot}
cp -ax /{bin,etc,mnt,sbin,lib,lib64} /tmp/tmproot/
cp -ax /usr/{bin,sbin,lib,lib64} /tmp/tmproot/usr/
cp -ax /var/{lib,local,lock,opt,run,spool,tmp} /tmp/tmproot/var/
cp -Rax /home /tmp/tmproot/

# Copy new image to tmpfs
wget https://geo.mirror.pkgbuild.com/images/latest/Arch-Linux-x86_64-cloudimg.qcow2 \
  -P /tmp/tmproot

# Switch root to tmpfs
mount --make-rprivate /
pivot_root /tmp/tmproot /tmp/tmproot/oldroot

# Move system mounts to tmpfs
for i in dev proc sys run; do mount --move /oldroot/$i /$i; done

# Restart services within the ramroot
systemctl restart sshd
systemctl list-units \
  --type=service \
  --state=running \
  --no-pager \
  --no-legend \
  | awk '!/ssh/ {print $1}' \
  | xargs systemctl restart
systemctl daemon-reexec

# Create and enable systemd service
cat << 'EOF' > /etc/systemd/system/arch_conversion.service
[Unit]
Description=Arch Linux Conversion
After=network.target

[Service]
Type=oneshot
ExecStart=/bin/bash /tmp/arch_conversion.sh
RemainAfterExit=yes

[Install]
WantedBy=multi-user.target
EOF

cat << 'EOF' > /tmp/arch_conversion.sh
#!/bin/bash

# Arch Linux conversion script
fuser -vkm /oldroot
umount -l /oldroot/
sleep 5
qemu-img convert -f qcow2 -O raw /Arch-Linux-x86_64-cloudimg.qcow2 /dev/vda
sleep 5
reboot
EOF

chmod +x /tmp/arch_conversion.sh
systemctl daemon-reload
systemctl enable arch_conversion.service

# Start the service
systemctl start arch_conversion.service