Spotter-VM/lxc-build

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#!/usr/bin/python3
import os
import shutil
import subprocess
import sys
LXC_ROOT = '/var/lib/lxc'
CONFIG_TEMPLATE = '''# Image name
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lxc.uts.name = {name}
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# Network
lxc.net.0.type = veth
lxc.net.0.link = lxcbr0
lxc.net.0.flags = up
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lxc.net.0.ipv4.address = 172.17.0.254/16
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lxc.net.0.ipv4.gateway = auto
# Volumes
lxc.rootfs.path = {rootfs}
# Mounts
lxc.mount.entry = /etc/hosts etc/hosts none bind 0 0
lxc.mount.entry = /etc/resolv.conf etc/resolv.conf none bind 0 0
{mounts}
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# Init
lxc.init.cmd = {cmd}
lxc.init.uid = {uid}
lxc.init.gid = {gid}
# Halt
lxc.signal.halt = SIGTERM
# Other
lxc.arch = x86_64
lxc.cap.drop = sys_admin
lxc.include = /usr/share/lxc/config/alpine.common.conf
'''
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class LXCImage:
def __init__(self, build_path):
self.name = None
self.layers = []
self.mounts = []
self.uid = 0
self.gid = 0
self.cmd = '/bin/true'
if os.path.isfile(build_path):
self.lxcfile = os.path.realpath(build_path)
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self.build_dir = os.path.dirname(self.lxcfile)
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else:
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self.build_dir = os.path.realpath(build_path)
self.lxcfile = os.path.join(self.build_dir, 'lxcfile')
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def build(self):
with open(self.lxcfile, 'r') as fd:
lxcfile = [l.strip() for l in fd.readlines()]
in_script = False
script = []
for line in lxcfile:
if line == 'RUN':
in_script = False
self.run_script(script)
elif in_script:
script.append(line)
elif line == 'SCRIPT':
script = []
in_script = True
elif line.startswith('IMAGE'):
self.set_name(line.split()[1])
elif line.startswith('LAYER'):
self.add_layer(line.split()[1])
elif line.startswith('COPY'):
srcdst = line.split()
self.copy_files(srcdst[1], srcdst[2] if len(srcdst) == 3 else '')
elif line.startswith('MOUNT'):
srcdst = line.split()
self.add_mount(srcdst[1], srcdst[2])
elif line.startswith('USER'):
uidgid = line.split()
self.set_user(uidgid[1], uidgid[2])
elif line.startswith('CMD'):
self.set_cmd(line.split()[1])
# Add the final layer which can be treated as nonpersistent
self.add_layer('{}/delta0'.format(self.name))
def rebuild_config(self):
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if len(self.layers) == 1:
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rootfs_path = layers[0]
else:
# Multiple lower overlayfs layers are ordered from right to left (lower2:lower1:rootfs:upper)
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rootfs_path = 'overlay:{}:{}'.format(':'.join(self.layers[:-1][::-1], self.layers[-1]))
mount_entries = '\n'.join(['lxc.mount.entry = {} none bind 0 0'.format(m) for m in self.mounts])
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with open(os.path.join(LXC_ROOT, self.name, 'config'), 'w') as fd:
fd.write(CONFIG_TEMPLATE.format(name=self.name, rootfs=rootfs_path, mounts=mount_entries, uid=self.uid, gid=self.gid, cmd=self.cmd))
def run_script(self, script):
sh = os.path.join(self.layers[-1], 'run.sh')
with open(sh, 'w') as fd:
fd.write('#!/bin/sh\nset -ev\n\n{}\n'.format('\n'.join(script)))
os.chmod(sh, 0o700)
subprocess.run(['lxc-execute', '-n', self.name, '--', '/bin/sh', '-lc', '/run.sh'], check=True)
os.unlink(sh)
def set_name(self, name):
self.name = name
os.makedirs(os.path.join(LXC_ROOT, self.name), 0o755, True)
self.rebuild_config()
def add_layer(self, layer):
layer = os.path.join(LXC_ROOT, layer)
self.layers.append(layer)
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os.makedirs(layer, 0o755, True)
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self.rebuild_config()
def copy_files(self, src, dst):
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src = os.path.join(build_dir, src)
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dst = os.path.join(layers[-1], dst)
copy_tree(src, dst)
def add_mount(self, src, dst):
mounts.append('{} {}'.format(src, dst))
self.rebuild_config()
def set_user(self, uid, gid):
self.uid = uid
self.gid = gid
self.rebuild_config()
def set_cmd(self, cmd):
self.cmd = cmd
self.rebuild_config()
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def copy_tree(src, dst):
if not os.path.isdir(src):
shutil.copy2(src, dst)
else:
os.makedirs(dst, exist_ok=True)
for name in os.listdir(src):
copy_tree(os.path.join(src, name), os.path.join(dst, name))
shutil.copystat(src, dst)
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# def fix_world():
# world_items = []
# last_world = []
# for layer in layers[:-1]:
# with open(os.path.join(layer, 'etc/apk/world'), 'r') as fd:
# last_world = fd.read().splitlines()
# world_items.extend(last_world)
# world_items = sorted(set(world_items))
# if world_items != sorted(last_world):
# os.makedirs(os.path.join(layers[-1], 'etc/apk', 0o755, True))
# with open(os.path.join(layers[-1], 'etc/apk/world'), 'w') as fd:
# fd.writelines(world_items)
if __name__ == '__main__':
if len(sys.argv) != 2:
print('Usage: lxc-build <buildpath>\n where the buildpath can be either specific lxcfile or a directory containing one')
else:
i = LXCImage(sys.argv[1])
i.build()