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pvc/client-api/provisioner/examples/debootstrap_script.py

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#!/usr/bin/env python3
# debootstrap_script.py - PVC Provisioner example script for Debootstrap
# Part of the Parallel Virtual Cluster (PVC) system
#
# Copyright (C) 2018-2020 Joshua M. Boniface <joshua@boniface.me>
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program. If not, see <https://www.gnu.org/licenses/>.
#
###############################################################################
# This script provides an example of a PVC provisioner script. It will install
# a Debian system, of the release specified in the keyword argument `deb_release`
# and from the mirror specified in the keyword argument `deb_mirror`, and
# including the packages specified in the keyword argument `deb_packages` (a list
# of strings, which is then joined together as a CSV and passed to debootstrap),
# to the configured disks, configure fstab, and install GRUB. Any later config
# should be done within the VM, for instance via cloud-init.
# This script can thus be used as an example or reference implementation of a
# PVC provisioner script and expanded upon as required.
# This script will run under root privileges as the provisioner does. Be careful
# with that.
import os
# Installation function - performs a debootstrap install of a Debian system
# Note that the only arguments are keyword arguments.
def install(**kwargs):
# The provisioner has already mounted the disks on kwargs['temporary_directory'].
# by this point, so we can get right to running the debootstrap after setting
# some nicer variable names; you don't necessarily have to do this.
vm_name = kwargs['vm_name']
temporary_directory = kwargs['temporary_directory']
disks = kwargs['disks']
networks = kwargs['networks']
# Our own required arguments. We should, though are not required to, handle
# failures of these gracefully, should administrators forget to specify them.
try:
deb_release = kwargs['deb_release']
except:
deb_release = "stable"
try:
deb_mirror = kwargs['deb_mirror']
except:
deb_mirror = "http://ftp.debian.org/debian"
try:
deb_packages = kwargs['deb_packages'].split(',')
except:
deb_packages = ["linux-image-amd64", "grub-pc", "cloud-init", "python3-cffi-backend", "wget"]
# We need to know our root disk
root_disk = None
for disk in disks:
if disk['mountpoint'] == '/':
root_disk = disk
if not root_disk:
return
# Ensure we have debootstrap intalled on the provisioner system; this is a
# good idea to include if you plan to use anything that is not part of the
# base Debian host system, just in case the provisioner host is not properly
# configured already.
os.system(
"apt-get install -y debootstrap"
)
# Perform a deboostrap installation
os.system(
"debootstrap --include={pkgs} {suite} {target} {mirror}".format(
suite=deb_release,
target=temporary_directory,
mirror=deb_mirror,
pkgs=','.join(deb_packages)
)
)
# Bind mount the devfs
os.system(
"mount --bind /dev {}/dev".format(
temporary_directory
)
)
# Create an fstab entry for each disk
fstab_file = "{}/etc/fstab".format(temporary_directory)
# The disk ID starts at zero and increments by one for each disk in the fixed-order
# disk list. This lets us work around the insanity of Libvirt IDs not matching guest IDs,
# while still letting us have some semblance of control here without enforcing things
# like labels. It increments in the for loop below at the end of each iteration, and is
# used to craft a /dev/disk/by-id/scsi-0QEMU_QEMU_HARDDISK_drive-scsi0-0-0-X device ID
# which will always match the correct order from Libvirt (unlike sdX/vdX names).
disk_id = 0
for disk in disks:
# We assume SSD-based/-like storage, and dislike atimes
options = "defaults,discard,noatime,nodiratime"
# The root, var, and log volumes have specific values
if disk['mountpoint'] == "/":
dump = 0
cpass = 1
elif disk['mountpoint'] == '/var' or disk['mountpoint'] == '/var/log':
dump = 0
cpass = 2
else:
dump = 0
cpass = 0
# Append the fstab line
with open(fstab_file, 'a') as fh:
data = "/dev/disk/by-id/scsi-0QEMU_QEMU_HARDDISK_drive-scsi0-0-0-{disk} {mountpoint} {filesystem} {options} {dump} {cpass}\n".format(
disk=disk_id,
mountpoint=disk['mountpoint'],
filesystem=disk['filesystem'],
options=options,
dump=dump,
cpass=cpass
)
fh.write(data)
# Increment the disk_id
disk_id += 1
# Write the hostname
hostname_file = "{}/etc/hostname".format(temporary_directory)
with open(hostname_file, 'w') as fh:
fh.write("{}".format(vm_name))
# Fix the cloud-init.target since it's broken
cloudinit_target_file = "{}/etc/systemd/system/cloud-init.target".format(temporary_directory)
with open(cloudinit_target_file, 'w') as fh:
data = """[Install]
WantedBy=multi-user.target
[Unit]
Description=Cloud-init target
After=multi-user.target
"""
fh.write(data)
# NOTE: Due to device ordering within the Libvirt XML configuration, the first Ethernet interface
# will always be on PCI bus ID 2, hence the name "ens2".
# Write a DHCP stanza for ens2
ens2_network_file = "{}/etc/network/interfaces.d/ens2".format(temporary_directory)
with open(ens2_network_file, 'w') as fh:
data = """auto ens2
iface ens2 inet dhcp
"""
fh.write(data)
# Write the DHCP config for ens2
dhclient_file = "{}/etc/dhcp/dhclient.conf".format(temporary_directory)
with open(dhclient_file, 'w') as fh:
data = """# DHCP client configuration
# Written by the PVC provisioner
option rfc3442-classless-static-routes code 121 = array of unsigned integer 8;
interface "ens2" {
""" + """ send fqdn.fqdn = "{hostname}";
send host-name = "{hostname}";
""".format(hostname=vm_name) + """ request subnet-mask, broadcast-address, time-offset, routers,
domain-name, domain-name-servers, domain-search, host-name,
dhcp6.name-servers, dhcp6.domain-search, dhcp6.fqdn, dhcp6.sntp-servers,
netbios-name-servers, netbios-scope, interface-mtu,
rfc3442-classless-static-routes, ntp-servers;
}
"""
fh.write(data)
# Write the GRUB configuration
grubcfg_file = "{}/etc/default/grub".format(temporary_directory)
with open(grubcfg_file, 'w') as fh:
data = """# Written by the PVC provisioner
GRUB_DEFAULT=0
GRUB_TIMEOUT=1
GRUB_DISTRIBUTOR="PVC Virtual Machine"
GRUB_CMDLINE_LINUX_DEFAULT="root=/dev/{root_disk} console=tty0 console=ttyS0,115200n8"
GRUB_CMDLINE_LINUX=""
GRUB_TERMINAL=console
GRUB_SERIAL_COMMAND="serial --speed=115200 --unit=0 --word=8 --parity=no --stop=1"
GRUB_DISABLE_LINUX_UUID=false
""".format(root_disk=root_disk['disk_id'])
fh.write(data)
# Chroot, do some in-root tasks, then exit the chroot
# EXITING THE CHROOT IS VERY IMPORTANT OR THE FOLLOWING STAGES OF THE PROVISIONER
# WILL FAIL IN UNEXPECTED WAYS! Keep this in mind when using chroot in your scripts.
real_root = os.open("/", os.O_RDONLY)
os.chroot(temporary_directory)
fake_root = os.open("/", os.O_RDONLY)
os.fchdir(fake_root)
# Install and update GRUB
os.system(
"grub-install --force /dev/rbd/{}/{}_{}".format(root_disk['pool'], vm_name, root_disk['disk_id'])
)
os.system(
"update-grub"
)
# Set a really dumb root password [TEMPORARY]
os.system(
"echo root:test123 | chpasswd"
)
# Enable cloud-init target on (first) boot
# NOTE: Your user-data should handle this and disable it once done, or things get messy.
# That cloud-init won't run without this hack seems like a bug... but even the official
# Debian cloud images are affected, so who knows.
os.system(
"systemctl enable cloud-init.target"
)
# Restore our original root/exit the chroot
# EXITING THE CHROOT IS VERY IMPORTANT OR THE FOLLOWING STAGES OF THE PROVISIONER
# WILL FAIL IN UNEXPECTED WAYS! Keep this in mind when using chroot in your scripts.
os.fchdir(real_root)
os.chroot(".")
os.fchdir(real_root)
os.close(fake_root)
os.close(real_root)
# Unmount the bound devfs
os.system(
"umount {}/dev".format(
temporary_directory
)
)
# Clean up file handles so paths can be unmounted
del fake_root
del real_root
# Everything else is done via cloud-init user-data
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