Use of a Linux initramfs to fully automate the bootstrapping process
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#!/usr/bin/env python3
This file contains a few functions to be shared by all Sys* classes
# SPDX-FileCopyrightText: 2021 fosslinux <>
# SPDX-FileCopyrightText: 2021 Andrius Štikonas <>
# SPDX-License-Identifier: GPL-3.0-or-later
import os
import hashlib
import shutil
import glob
import subprocess
import requests
from lib.utils import mount, umount, get_target, copytree
class SysGeneral:
A class from which all Sys* class are extended.
Contains functions used in all Sys*
# All of these are variables defined in the individual Sys* classes
preserve_tmp = None
tmp_dir = None
base_dir = None
git_dir = None
sys_dir = None
initramfs_path = None
def __del__(self):
if not self.preserve_tmp:
print(f"Unmounting tmpfs from {self.tmp_dir}")
def mount_tmpfs(self):
"""Mount the tmpfs for this sysx"""
if not os.path.isdir(self.tmp_dir):
print(f"Mounting tmpfs on {self.tmp_dir}")
mount('tmpfs', self.tmp_dir, 'tmpfs', 'size=8G')
def check_file(self, file_name):
"""Check hash of downloaded source file."""
checksum_store = os.path.join(self.git_dir, 'SHA256SUMS.sources')
with open(checksum_store, encoding="utf_8") as checksum_file:
hashes =
for hash_line in hashes:
if os.path.basename(file_name) in hash_line:
# Hash is in store, check it
expected_hash = hash_line.split()[0]
with open(file_name, "rb") as downloaded_file:
downloaded_content = # read entire file as bytes
readable_hash = hashlib.sha256(downloaded_content).hexdigest()
if expected_hash == readable_hash:
raise Exception("Checksum mismatch")
raise Exception("File checksum is not yet recorded")
def download_file(self, url, file_name=None):
Download a single source archive.
cache_dir = os.path.join(self.git_dir, 'sources')
# Automatically determine file name based on URL.
if file_name is None:
file_name = os.path.basename(url)
abs_file_name = os.path.join(cache_dir, file_name)
# Create a cache directory for downloaded sources
if not os.path.isdir(cache_dir):
# Actually download the file
if not os.path.isfile(abs_file_name):
print(f"Downloading: {file_name}")
response = requests.get(url, allow_redirects=True, stream=True)
if response.status_code == 200:
with open(abs_file_name, 'wb') as target_file:
raise Exception("Download failed.")
# Check SHA256 hash
return abs_file_name
def get_file(self, url, mkbuild=False, output=None):
Download and prepare source packages
url can be either:
1. a single URL
2. list of URLs to download. In this case the first URL is the primary URL
from which we derive the name of package directory
output can be used to override file name of the downloaded file(s).
mkbuild=True can be used to pre-create build directories before
mkdir is available.
# Single URL
if isinstance(url, str):
assert output is None or isinstance(output, str)
file_name = url if output is None else output
urls = [url]
outputs = [output]
# Multiple URLs
elif isinstance(url, list):
assert output is None or len(output) == len(url)
file_name = url[0] if output is None else output[0]
urls = url
outputs = output if output is not None else [None] * len(url)
raise TypeError("url must be either a string or a list of strings")
# Determine installation directory
target_name = get_target(file_name)
target_src_dir = os.path.join(self.base_dir, target_name, 'src')
# Install base files
src_tree = os.path.join(self.sys_dir, target_name)
copytree(src_tree, self.base_dir)
if not os.path.isdir(target_src_dir):
for i, _ in enumerate(urls):
# Download files into cache directory
tarball = self.download_file(urls[i], outputs[i])
# Install sources into target directory
shutil.copy2(tarball, target_src_dir)
if mkbuild:
os.mkdir(os.path.join(self.base_dir, target_name, 'build'))
def deploy_sysglobal_files(self):
"""Deploy files common to all Sys*"""
sysglobal_files = ['bootstrap.cfg', '']
for file in sysglobal_files:
shutil.copy2(os.path.join(self.git_dir, 'sysglobal', file),
def make_initramfs(self):
"""Package binary bootstrap seeds and sources into initramfs."""
self.initramfs_path = os.path.join(self.tmp_dir, 'initramfs')
# Create a list of files to go within the initramfs
file_list = glob.glob(os.path.join(self.tmp_dir, '**'), recursive=True)
# Use built-in removeprefix once we can use Python 3.9
def remove_prefix(text, prefix):
if text.startswith(prefix):
return text[len(prefix):]
return text # or whatever
file_list = [remove_prefix(f, self.tmp_dir + os.sep) for f in file_list]
# Create the initramfs
with open(self.initramfs_path, "w", encoding="utf_8") as initramfs:
# pylint: disable=consider-using-with
cpio = subprocess.Popen(
["cpio", "--format", "newc", "--create",
"--directory", self.tmp_dir],
stdin=subprocess.PIPE, stdout=initramfs)