# imgutils.py - utility functions/classes for building disk images
#
# Copyright (C) 2011-2015 Red Hat, Inc.
#
# 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 2 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 <http://www.gnu.org/licenses/>.
#
# Author(s): Will Woods <wwoods@redhat.com>
import logging
logger = logging.getLogger("pylorax.imgutils")
import os, tempfile
from os.path import join, dirname
from subprocess import Popen, PIPE, CalledProcessError
import sys
import traceback
import multiprocessing
from time import sleep
from pylorax.sysutils import cpfile
from pylorax.executils import execWithRedirect, execWithCapture
from pylorax.executils import runcmd, runcmd_output
######## Functions for making container images (cpio, tar, squashfs) ##########
[docs]def compress(command, rootdir, outfile, compression="xz", compressargs=None):
'''Make a compressed archive of the given rootdir.
command is a list of the archiver commands to run
compression should be "xz", "gzip", "lzma", "bzip2", or None.
compressargs will be used on the compression commandline.'''
if compression not in (None, "xz", "gzip", "lzma", "bzip2"):
raise ValueError("Unknown compression type %s" % compression)
compressargs = compressargs or ["-9"]
if compression == "xz":
compressargs.insert(0, "--check=crc32")
if compression is None:
compression = "cat" # this is a little silly
compressargs = []
# make compression run with multiple threads if possible
if compression in ("xz", "lzma"):
compressargs.insert(0, "-T%d" % multiprocessing.cpu_count())
elif compression == "gzip":
compression = "pigz"
compressargs.insert(0, "-p%d" % multiprocessing.cpu_count())
elif compression == "bzip2":
compression = "pbzip2"
compressargs.insert(0, "-p%d" % multiprocessing.cpu_count())
logger.debug("find %s -print0 |%s | %s %s > %s", rootdir, " ".join(command),
compression, " ".join(compressargs), outfile)
find, archive, comp = None, None, None
try:
find = Popen(["find", ".", "-print0"], stdout=PIPE, cwd=rootdir)
archive = Popen(command, stdin=find.stdout, stdout=PIPE, cwd=rootdir)
comp = Popen([compression] + compressargs,
stdin=archive.stdout, stdout=open(outfile, "wb"))
comp.wait()
return comp.returncode
except OSError as e:
logger.error(e)
# Kill off any hanging processes
list(p.kill() for p in (find, archive, comp) if p)
return 1
[docs]def mkcpio(rootdir, outfile, compression="xz", compressargs=None):
compressargs = compressargs or ["-9"]
return compress(["cpio", "--null", "--quiet", "-H", "newc", "-o"],
rootdir, outfile, compression, compressargs)
[docs]def mktar(rootdir, outfile, compression="xz", compressargs=None):
compressargs = compressargs or ["-9"]
return compress(["tar", "--no-recursion", "--selinux", "--acls", "--xattrs", "-cf-", "--null", "-T-"],
rootdir, outfile, compression, compressargs)
[docs]def mksquashfs(rootdir, outfile, compression="default", compressargs=None):
'''Make a squashfs image containing the given rootdir.'''
compressargs = compressargs or []
if compression != "default":
compressargs = ["-comp", compression] + compressargs
return execWithRedirect("mksquashfs", [rootdir, outfile] + compressargs)
[docs]def mkrootfsimg(rootdir, outfile, label, size=2, sysroot=""):
"""
Make rootfs image from a directory
:param str rootdir: Root directory
:param str outfile: Path of output image file
:param str label: Filesystem label
:param int size: Size of the image in GiB, if None computed automatically
:param str sysroot: path to system (deployment) root relative to physical root
"""
if size:
fssize = size * (1024*1024*1024) # 2GB sparse file compresses down to nothin'
else:
fssize = None # Let mkext4img figure out the needed size
mkext4img(rootdir, outfile, label=label, size=fssize)
# Reset selinux context on new rootfs
with LoopDev(outfile) as loopdev:
with Mount(loopdev) as mnt:
cmd = [ "setfiles", "-e", "/proc", "-e", "/sys", "-e", "/dev", "-e", "/install",
"/etc/selinux/targeted/contexts/files/file_contexts", "/"]
root = join(mnt, sysroot.lstrip("/"))
runcmd(cmd, root=root)
######## Utility functions ###############################################
[docs]def mksparse(outfile, size):
'''use os.ftruncate to create a sparse file of the given size.'''
fobj = open(outfile, "w")
os.ftruncate(fobj.fileno(), size)
[docs]def mkqcow2(outfile, size, options=None):
'''use qemu-img to create a file of the given size.
options is a list of options passed to qemu-img
Default format is qcow2, override by passing "-f", fmt
in options.
'''
options = options or []
if "-f" not in options:
options.extend(["-f", "qcow2"])
runcmd(["qemu-img", "create"] + options + [outfile, str(size)])
[docs]def loop_attach(outfile):
'''Attach a loop device to the given file. Return the loop device name.
Raises CalledProcessError if losetup fails.'''
dev = runcmd_output(["losetup", "--find", "--show", outfile])
return dev.strip()
[docs]def loop_detach(loopdev):
'''Detach the given loop device. Return False on failure.'''
return (execWithRedirect("losetup", ["--detach", loopdev]) == 0)
[docs]def get_loop_name(path):
'''Return the loop device associated with the path.
Raises RuntimeError if more than one loop is associated'''
buf = runcmd_output(["losetup", "-j", path])
if len(buf.splitlines()) > 1:
# there should never be more than one loop device listed
raise RuntimeError("multiple loops associated with %s" % path)
name = os.path.basename(buf.split(":")[0])
return name
[docs]def dm_attach(dev, size, name=None):
'''Attach a devicemapper device to the given device, with the given size.
If name is None, a random name will be chosen. Returns the device name.
raises CalledProcessError if dmsetup fails.'''
if name is None:
name = tempfile.mktemp(prefix="lorax.imgutils.", dir="")
runcmd(["dmsetup", "create", name, "--table",
"0 %i linear %s 0" % (size/512, dev)])
return name
[docs]def dm_detach(dev):
'''Detach the named devicemapper device. Returns False if dmsetup fails.'''
dev = dev.replace("/dev/mapper/", "") # strip prefix, if it's there
return execWithRedirect("dmsetup", ["remove", dev])
[docs]def mount(dev, opts="", mnt=None):
'''Mount the given device at the given mountpoint, using the given opts.
opts should be a comma-separated string of mount options.
if mnt is none, a temporary directory will be created and its path will be
returned.
raises CalledProcessError if mount fails.'''
if mnt is None:
mnt = tempfile.mkdtemp(prefix="lorax.imgutils.")
logger.debug("make tmp mountdir %s", mnt)
cmd = ["mount"]
if opts:
cmd += ["-o", opts]
cmd += [dev, mnt]
runcmd(cmd)
return mnt
[docs]def umount(mnt, lazy=False, maxretry=3, retrysleep=1.0):
'''Unmount the given mountpoint. If lazy is True, do a lazy umount (-l).
If the mount was a temporary dir created by mount, it will be deleted.
raises CalledProcessError if umount fails.'''
cmd = ["umount"]
if lazy: cmd += ["-l"]
cmd += [mnt]
count = 0
while maxretry > 0:
try:
rv = runcmd(cmd)
except CalledProcessError:
count += 1
if count == maxretry:
raise
logger.warn("failed to unmount %s. retrying (%d/%d)...",
mnt, count, maxretry)
if logger.getEffectiveLevel() <= logging.DEBUG:
fuser = execWithCapture("fuser", ["-vm", mnt])
logger.debug("fuser -vm:\n%s\n", fuser)
sleep(retrysleep)
else:
break
if 'lorax.imgutils' in mnt:
os.rmdir(mnt)
logger.debug("remove tmp mountdir %s", mnt)
return (rv == 0)
[docs]def copytree(src, dest, preserve=True):
'''Copy a tree of files using cp -a, thus preserving modes, timestamps,
links, acls, sparse files, xattrs, selinux contexts, etc.
If preserve is False, uses cp -R (useful for modeless filesystems)
raises CalledProcessError if copy fails.'''
logger.debug("copytree %s %s", src, dest)
cp = ["cp", "-a"] if preserve else ["cp", "-R", "-L"]
cp += [join(src, "."), os.path.abspath(dest)]
runcmd(cp)
[docs]def do_grafts(grafts, dest, preserve=True):
'''Copy each of the items listed in grafts into dest.
If the key ends with '/' it's assumed to be a directory which should be
created, otherwise just the leading directories will be created.'''
for imgpath, filename in grafts.items():
if imgpath[-1] == '/':
targetdir = join(dest, imgpath)
imgpath = imgpath[:-1]
else:
targetdir = join(dest, dirname(imgpath))
if not os.path.isdir(targetdir):
os.makedirs(targetdir)
if os.path.isdir(filename):
copytree(filename, join(dest, imgpath), preserve)
else:
cpfile(filename, join(dest, imgpath))
[docs]def round_to_blocks(size, blocksize):
'''If size isn't a multiple of blocksize, round up to the next multiple'''
diff = size % blocksize
if diff or not size:
size += blocksize - diff
return size
# TODO: move filesystem data outside this function
[docs]def estimate_size(rootdir, graft=None, fstype=None, blocksize=4096, overhead=128):
graft = graft or {}
getsize = lambda f: os.lstat(f).st_size
if fstype == "btrfs":
overhead = 64*1024 # don't worry, it's all sparse
if fstype == "hfsplus":
overhead = 200 # hack to deal with two bootloader copies
if fstype in ("vfat", "msdos"):
blocksize = 2048
getsize = lambda f: os.stat(f).st_size # no symlinks, count as copies
total = overhead*blocksize
dirlist = list(graft.values())
if rootdir:
dirlist.append(rootdir)
for root in dirlist:
for top, dirs, files in os.walk(root):
for f in files + dirs:
total += round_to_blocks(getsize(join(top,f)), blocksize)
if fstype == "btrfs":
total = max(256*1024*1024, total) # btrfs minimum size: 256MB
return total
######## Execution contexts - use with the 'with' statement ##############
[docs]class LoopDev(object):
def __init__(self, filename, size=None):
self.loopdev = None
self.filename = filename
if size:
mksparse(self.filename, size)
def __enter__(self):
self.loopdev = loop_attach(self.filename)
return self.loopdev
def __exit__(self, exc_type, exc_value, tracebk):
loop_detach(self.loopdev)
[docs]class DMDev(object):
def __init__(self, dev, size, name=None):
self.mapperdev = None
(self.dev, self.size, self.name) = (dev, size, name)
def __enter__(self):
self.mapperdev = dm_attach(self.dev, self.size, self.name)
return self.mapperdev
def __exit__(self, exc_type, exc_value, tracebk):
dm_detach(self.mapperdev)
[docs]class Mount(object):
def __init__(self, dev, opts="", mnt=None):
(self.dev, self.opts, self.mnt) = (dev, opts, mnt)
def __enter__(self):
self.mnt = mount(self.dev, self.opts, self.mnt)
return self.mnt
def __exit__(self, exc_type, exc_value, tracebk):
umount(self.mnt)
[docs]class PartitionMount(object):
""" Mount a partitioned image file using kpartx """
def __init__(self, disk_img, mount_ok=None):
"""
disk_img is the full path to a partitioned disk image
mount_ok is a function that is passed the mount point and
returns True if it should be mounted.
"""
self.mount_dev = None
self.mount_size = None
self.mount_dir = None
self.disk_img = disk_img
self.mount_ok = mount_ok
# Default is to mount partition with /etc/passwd
if not self.mount_ok:
self.mount_ok = lambda mount_dir: os.path.isfile(mount_dir+"/etc/passwd")
# Example kpartx output
# kpartx -p p -v -a /tmp/diskV2DiCW.im
# add map loop2p1 (253:2): 0 3481600 linear /dev/loop2 2048
# add map loop2p2 (253:3): 0 614400 linear /dev/loop2 3483648
kpartx_output = runcmd_output(["kpartx", "-v", "-a", "-s", self.disk_img])
logger.debug(kpartx_output)
# list of (deviceName, sizeInBytes)
self.loop_devices = []
for line in kpartx_output.splitlines():
# add map loop2p3 (253:4): 0 7139328 linear /dev/loop2 528384
# 3rd element is size in 512 byte blocks
if line.startswith("add map "):
fields = line[8:].split()
self.loop_devices.append( (fields[0], int(fields[3])*512) )
def __enter__(self):
# Mount the device selected by mount_ok, if possible
mount_dir = tempfile.mkdtemp()
for dev, size in self.loop_devices:
try:
mount( "/dev/mapper/"+dev, mnt=mount_dir )
if self.mount_ok(mount_dir):
self.mount_dir = mount_dir
self.mount_dev = dev
self.mount_size = size
break
umount( mount_dir )
except CalledProcessError:
logger.debug(traceback.format_exc())
if self.mount_dir:
logger.info("Partition mounted on %s size=%s", self.mount_dir, self.mount_size)
else:
logger.debug("Unable to mount anything from %s", self.disk_img)
os.rmdir(mount_dir)
return self
def __exit__(self, exc_type, exc_value, tracebk):
if self.mount_dir:
umount( self.mount_dir )
os.rmdir(self.mount_dir)
self.mount_dir = None
execWithRedirect("kpartx", ["-d", "-s", self.disk_img])
######## Functions for making filesystem images ##########################
[docs]def mkfsimage(fstype, rootdir, outfile, size=None, mkfsargs=None, mountargs="", graft=None):
'''Generic filesystem image creation function.
fstype should be a filesystem type - "mkfs.${fstype}" must exist.
graft should be a dict: {"some/path/in/image": "local/file/or/dir"};
if the path ends with a '/' it's assumed to be a directory.
Will raise CalledProcessError if something goes wrong.'''
mkfsargs = mkfsargs or []
graft = graft or {}
preserve = (fstype not in ("msdos", "vfat"))
if not size:
size = estimate_size(rootdir, graft, fstype)
with LoopDev(outfile, size) as loopdev:
try:
runcmd(["mkfs.%s" % fstype] + mkfsargs + [loopdev])
except CalledProcessError as e:
logger.error("mkfs exited with a non-zero return code: %d", e.returncode)
logger.error(e.output)
sys.exit(e.returncode)
with Mount(loopdev, mountargs) as mnt:
if rootdir:
copytree(rootdir, mnt, preserve)
do_grafts(graft, mnt, preserve)
# Make absolutely sure that the data has been written
runcmd(["sync"])
# convenience functions with useful defaults
[docs]def mkdosimg(rootdir, outfile, size=None, label="", mountargs="shortname=winnt,umask=0077", graft=None):
graft = graft or {}
mkfsimage("msdos", rootdir, outfile, size, mountargs=mountargs,
mkfsargs=["-n", label], graft=graft)
[docs]def mkext4img(rootdir, outfile, size=None, label="", mountargs="", graft=None):
graft = graft or {}
mkfsimage("ext4", rootdir, outfile, size, mountargs=mountargs,
mkfsargs=["-L", label, "-b", "1024", "-m", "0"], graft=graft)
[docs]def mkbtrfsimg(rootdir, outfile, size=None, label="", mountargs="", graft=None):
graft = graft or {}
mkfsimage("btrfs", rootdir, outfile, size, mountargs=mountargs,
mkfsargs=["-L", label], graft=graft)
[docs]def mkhfsimg(rootdir, outfile, size=None, label="", mountargs="", graft=None):
graft = graft or {}
mkfsimage("hfsplus", rootdir, outfile, size, mountargs=mountargs,
mkfsargs=["-v", label], graft=graft)