d6280b9cf0
Allow passing of size to create_runtime, add PartitionMount context to use kpartx to mount partitioned file images. Add resetting the selinux context on the newly created rootfs.
293 lines
12 KiB
Python
293 lines
12 KiB
Python
# imgutils.py - utility functions/classes for building disk images
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#
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# Copyright (C) 2011 Red Hat, Inc.
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#
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# This program is free software; you can redistribute it and/or modify
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# it under the terms of the GNU General Public License as published by
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# the Free Software Foundation; either version 2 of the License, or
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# (at your option) any later version.
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#
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# This program is distributed in the hope that it will be useful,
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# but WITHOUT ANY WARRANTY; without even the implied warranty of
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# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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# GNU General Public License for more details.
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#
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# You should have received a copy of the GNU General Public License
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# along with this program. If not, see <http://www.gnu.org/licenses/>.
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#
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# Author(s): Will Woods <wwoods@redhat.com>
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import logging
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logger = logging.getLogger("pylorax.imgutils")
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import os, tempfile
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from os.path import join, dirname
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from pylorax.sysutils import cpfile
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from subprocess import *
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import traceback
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######## Functions for making container images (cpio, squashfs) ##########
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def mkcpio(rootdir, outfile, compression="xz", compressargs=["-9"]):
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'''Make a compressed CPIO archive of the given rootdir.
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compression should be "xz", "gzip", "lzma", or None.
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compressargs will be used on the compression commandline.'''
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if compression not in (None, "xz", "gzip", "lzma"):
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raise ValueError, "Unknown compression type %s" % compression
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chdir = lambda: os.chdir(rootdir)
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if compression == "xz":
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compressargs.insert(0, "--check=crc32")
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if compression is None:
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compression = "cat" # this is a little silly
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compressargs = []
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find = Popen(["find", ".", "-print0"], stdout=PIPE, preexec_fn=chdir)
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cpio = Popen(["cpio", "--null", "--quiet", "-H", "newc", "-o"],
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stdin=find.stdout, stdout=PIPE, preexec_fn=chdir)
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comp = Popen([compression] + compressargs,
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stdin=cpio.stdout, stdout=open(outfile, "wb"))
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comp.wait()
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return comp.returncode
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def mksquashfs(rootdir, outfile, compression="default", compressargs=[]):
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'''Make a squashfs image containing the given rootdir.'''
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if compression != "default":
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compressargs = ["-comp", compression] + compressargs
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return call(["mksquashfs", rootdir, outfile] + compressargs)
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######## Utility functions ###############################################
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def mksparse(outfile, size):
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'''use os.ftruncate to create a sparse file of the given size.'''
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fobj = open(outfile, "w")
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os.ftruncate(fobj.fileno(), size)
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def loop_attach(outfile):
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'''Attach a loop device to the given file. Return the loop device name.
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Raises CalledProcessError if losetup fails.'''
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dev = check_output(["losetup", "--find", "--show", outfile], stderr=PIPE)
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return dev.strip()
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def loop_detach(loopdev):
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'''Detach the given loop device. Return False on failure.'''
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return (call(["losetup", "--detach", loopdev]) == 0)
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def dm_attach(dev, size, name=None):
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'''Attach a devicemapper device to the given device, with the given size.
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If name is None, a random name will be chosen. Returns the device name.
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raises CalledProcessError if dmsetup fails.'''
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if name is None:
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name = tempfile.mktemp(prefix="lorax.imgutils.", dir="")
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check_call(["dmsetup", "create", name, "--table",
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"0 %i linear %s 0" % (size/512, dev)],
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stdout=PIPE, stderr=PIPE)
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return name
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def dm_detach(dev):
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'''Detach the named devicemapper device. Returns False if dmsetup fails.'''
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dev = dev.replace("/dev/mapper/", "") # strip prefix, if it's there
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return call(["dmsetup", "remove", dev], stdout=PIPE, stderr=PIPE)
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def mount(dev, opts="", mnt=None):
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'''Mount the given device at the given mountpoint, using the given opts.
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opts should be a comma-separated string of mount options.
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if mnt is none, a temporary directory will be created and its path will be
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returned.
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raises CalledProcessError if mount fails.'''
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if mnt is None:
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mnt = tempfile.mkdtemp(prefix="lorax.imgutils.")
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mount = ["mount"]
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if opts:
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mount += ["-o", opts]
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check_call(mount + [dev, mnt])
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return mnt
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def umount(mnt):
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'''Unmount the given mountpoint. If the mount was a temporary dir created
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by mount, it will be deleted. Returns false if the unmount fails.'''
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rv = call(["umount", mnt])
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if 'lorax.imgutils' in mnt:
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os.rmdir(mnt)
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return (rv == 0)
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def copytree(src, dest, preserve=True):
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'''Copy a tree of files using cp -a, thus preserving modes, timestamps,
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links, acls, sparse files, xattrs, selinux contexts, etc.
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If preserve is False, uses cp -R (useful for modeless filesystems)'''
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chdir = lambda: os.chdir(src)
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cp = ["cp", "-a"] if preserve else ["cp", "-R", "-L"]
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check_call(cp + [".", os.path.abspath(dest)], preexec_fn=chdir)
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def do_grafts(grafts, dest, preserve=True):
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'''Copy each of the items listed in grafts into dest.
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If the key ends with '/' it's assumed to be a directory which should be
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created, otherwise just the leading directories will be created.'''
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for imgpath, filename in grafts.items():
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if imgpath[-1] == '/':
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targetdir = join(dest, imgpath)
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imgpath = imgpath[:-1]
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else:
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targetdir = join(dest, dirname(imgpath))
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if not os.path.isdir(targetdir):
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os.makedirs(targetdir)
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if os.path.isdir(filename):
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copytree(filename, join(dest, imgpath), preserve)
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else:
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cpfile(filename, join(dest, imgpath))
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def round_to_blocks(size, blocksize):
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'''If size isn't a multiple of blocksize, round up to the next multiple'''
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diff = size % blocksize
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if diff or not size:
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size += blocksize - diff
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return size
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# TODO: move filesystem data outside this function
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def estimate_size(rootdir, graft={}, fstype=None, blocksize=4096, overhead=128):
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getsize = lambda f: os.lstat(f).st_size
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if fstype == "btrfs":
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overhead = 64*1024 # don't worry, it's all sparse
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if fstype in ("vfat", "msdos"):
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blocksize = 2048
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getsize = lambda f: os.stat(f).st_size # no symlinks, count as copies
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total = overhead*blocksize
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dirlist = graft.values()
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if rootdir:
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dirlist.append(rootdir)
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for root in dirlist:
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for top, dirs, files in os.walk(root):
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for f in files + dirs:
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total += round_to_blocks(getsize(join(top,f)), blocksize)
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if fstype == "btrfs":
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total = max(256*1024*1024, total) # btrfs minimum size: 256MB
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return total
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######## Execution contexts - use with the 'with' statement ##############
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class LoopDev(object):
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def __init__(self, filename, size=None):
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self.filename = filename
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if size:
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mksparse(self.filename, size)
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def __enter__(self):
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self.loopdev = loop_attach(self.filename)
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return self.loopdev
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def __exit__(self, exc_type, exc_value, traceback):
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loop_detach(self.loopdev)
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class DMDev(object):
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def __init__(self, dev, size, name=None):
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(self.dev, self.size, self.name) = (dev, size, name)
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def __enter__(self):
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self.mapperdev = dm_attach(self.dev, self.size, self.name)
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return self.mapperdev
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def __exit__(self, exc_type, exc_value, traceback):
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dm_detach(self.mapperdev)
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class Mount(object):
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def __init__(self, dev, opts="", mnt=None):
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(self.dev, self.opts, self.mnt) = (dev, opts, mnt)
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def __enter__(self):
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self.mnt = mount(self.dev, self.opts, self.mnt)
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return self.mnt
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def __exit__(self, exc_type, exc_value, traceback):
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umount(self.mnt)
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class PartitionMount(object):
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""" Mount a partitioned image file using kpartx """
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def __init__(self, disk_img, mount_ok=None):
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"""
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disk_img is the full path to a partitioned disk image
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mount_ok is a function that is passed the mount point and
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returns True if it should be mounted.
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"""
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self.mount_dir = None
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self.disk_img = disk_img
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self.mount_ok = mount_ok
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# Default is to mount partition with /etc/passwd
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if not self.mount_ok:
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self.mount_ok = lambda mount_dir: os.path.isfile(mount_dir+"/etc/passwd")
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# Example kpartx output
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# kpartx -p p -v -a /tmp/diskV2DiCW.im
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# add map loop2p1 (253:2): 0 3481600 linear /dev/loop2 2048
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# add map loop2p2 (253:3): 0 614400 linear /dev/loop2 3483648
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cmd = [ "kpartx", "-v", "-p", "p", "-a", self.disk_img ]
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logger.debug(cmd)
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kpartx_output = check_output(cmd)
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logger.debug(kpartx_output)
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# list of (deviceName, sizeInBytes)
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self.loop_devices = []
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for line in kpartx_output.splitlines():
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# add map loop2p3 (253:4): 0 7139328 linear /dev/loop2 528384
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# 3rd element is size in 512 byte blocks
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if line.startswith("add map "):
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fields = line[8:].split()
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self.loop_devices.append( (fields[0], int(fields[3])*512) )
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def __enter__(self):
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# Mount the device selected by mount_ok, if possible
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mount_dir = tempfile.mkdtemp()
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for dev, size in self.loop_devices:
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try:
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mount( "/dev/mapper/"+dev, mnt=mount_dir )
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if self.mount_ok(mount_dir):
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self.mount_dir = mount_dir
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self.mount_dev = dev
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self.mount_size = size
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break
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umount( mount_dir )
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except CalledProcessError:
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logger.debug(traceback.format_exc())
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if self.mount_dir:
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logger.info("Partition mounted on {0} size={1}".format(self.mount_dir, self.mount_size))
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else:
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logger.debug("Unable to mount anything from {0}".format(self.disk_img))
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os.rmdir(mount_dir)
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return self
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def __exit__(self, exc_type, exc_value, traceback):
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if self.mount_dir:
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umount( self.mount_dir )
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os.rmdir(self.mount_dir)
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self.mount_dir = None
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call(["kpartx", "-d", self.disk_img])
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######## Functions for making filesystem images ##########################
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def mkfsimage(fstype, rootdir, outfile, size=None, mkfsargs=[], mountargs="", graft={}):
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'''Generic filesystem image creation function.
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fstype should be a filesystem type - "mkfs.${fstype}" must exist.
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graft should be a dict: {"some/path/in/image": "local/file/or/dir"};
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if the path ends with a '/' it's assumed to be a directory.
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Will raise CalledProcessError if something goes wrong.'''
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preserve = (fstype not in ("msdos", "vfat"))
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if not size:
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size = estimate_size(rootdir, graft, fstype)
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with LoopDev(outfile, size) as loopdev:
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check_call(["mkfs.%s" % fstype] + mkfsargs + [loopdev],
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stdout=PIPE, stderr=PIPE)
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with Mount(loopdev, mountargs) as mnt:
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if rootdir:
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copytree(rootdir, mnt, preserve)
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do_grafts(graft, mnt, preserve)
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# convenience functions with useful defaults
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def mkdosimg(rootdir, outfile, size=None, label="", mountargs="shortname=winnt,umask=0077", graft={}):
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mkfsimage("msdos", rootdir, outfile, size, mountargs=mountargs,
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mkfsargs=["-n", label], graft=graft)
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def mkext4img(rootdir, outfile, size=None, label="", mountargs="", graft={}):
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mkfsimage("ext4", rootdir, outfile, size, mountargs=mountargs,
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mkfsargs=["-L", label, "-b", "1024", "-m", "0"], graft=graft)
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def mkbtrfsimg(rootdir, outfile, size=None, label="", mountargs="", graft={}):
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mkfsimage("btrfs", rootdir, outfile, size, mountargs=mountargs,
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mkfsargs=["-L", label], graft=graft)
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def mkhfsimg(rootdir, outfile, size=None, label="", mountargs="", graft={}):
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mkfsimage("hfs", rootdir, outfile, size, mountargs=mountargs,
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mkfsargs=["-v", label], graft=graft)
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