This adds a "btrsquash" style for ramdisks - a squashfs-compressed btrfs
image which gets loaded by the same dracut 'dmsquash-live' module used by
our LiveOS images.
This saves a good ~256MB RAM, which allows us to install on systems with
512MB RAM again.
---
src/pylorax/__init__.py | 5 ++
src/pylorax/constants.py | 2 +
src/pylorax/installtree.py | 102 ++++++++++++++++++++++++++++++++++++++++++++
3 files changed, 109 insertions(+), 0 deletions(-)
diff --git a/src/pylorax/__init__.py b/src/pylorax/__init__.py
index de74b28..a575031 100644
--- a/src/pylorax/__init__.py
+++ b/src/pylorax/__init__.py
@@ -283,6 +283,11 @@ class Lorax(BaseLoraxClass):
logger.info("moving stubs")
self.installtree.move_stubs()
+ # if needed: create initramfs (before modules get shuffled around)
+ if self.conf.get("ramdisk", "style") == "btrsquash":
+ logger.info("creating dracut initramfs")
+ self.installtree.make_squash_initramfs()
+
# get the list of required modules
logger.info("getting list of required modules")
modules = [f[1:] for f in template if f[0] == "module"]
diff --git a/src/pylorax/constants.py b/src/pylorax/constants.py
index 547a938..c46699f 100644
--- a/src/pylorax/constants.py
+++ b/src/pylorax/constants.py
@@ -47,7 +47,9 @@ class LoraxRequiredCommands(dict):
self["LOCALEDEF"] = "localedef"
self["LOSETUP"] = "losetup"
self["MKDOSFS"] = "mkdosfs"
+ self["MKFS_BTRFS"] = "mkfs.btrfs"
self["MKISOFS"] = "mkisofs"
+ self["MKSQUASHFS"] = "mksquashfs"
self["MODINFO"] = "modinfo"
self["MOUNT"] = "mount"
self["PARTED"] = "parted"
diff --git a/src/pylorax/installtree.py b/src/pylorax/installtree.py
index 9704769..60d6470 100644
--- a/src/pylorax/installtree.py
+++ b/src/pylorax/installtree.py
@@ -26,6 +26,7 @@ import sys
import os
import shutil
import gzip
+import lzma
import re
import glob
import time
@@ -52,6 +53,9 @@ class LoraxInstallTree(BaseLoraxClass):
if self.style == 'initramfs':
self.make_initrd = self.make_initramfs
+ if self.style == 'btrsquash':
+ self._mkfs = [self.lcmds.MKFS_BTRFS, "-L", "Anaconda"]
+ self.make_initrd = self.make_live_squashfs
def compress(self, initrd, kernel, compression="xz"):
start = time.time()
@@ -539,6 +543,104 @@ class LoraxInstallTree(BaseLoraxClass):
return True
+ def make_squash_initramfs(self):
+ outfile = "/tmp/initramfs.img"
+ logger.debug("chrooting into installtree to create initramfs.img")
+ # NOTE: ext[34] gets included by default, but we have to ask for btrfs
+ subprocess.check_call(["chroot", self.root,
+ "/sbin/dracut", "--nomdadmconf", "--nolvmconf",
+ "--modules", "base btrfs dmsquash-live",
+ outfile, self.kernels[0].version])
+ # move output file into installtree workdir, and repack with xz.
+ # NOTE: for some reason the concatenated image will fail to boot if we
+ # leave it gzipped? Weird.
+ self.initramfs = joinpaths(self.workdir, "initramfs.img")
+ gzip_in = gzip.open(joinpaths(self.root, outfile))
+ xz_out = lzma.LZMAFile(self.initramfs, "w",
+ options={'format':'xz', 'level':9})
+ xz_out.write(gzip_in.read())
+
+
+ def make_live_squashfs(self, initrd, kernel, compression):
+ '''This is a little complicated, but dracut wants to find a squashfs
+ image named "squashfs.img" which contains a filesystem image named
+ "LiveOS/rootfs.img".
+ Placing squashfs.img inside a cpio image and concatenating that
+ with the existing initramfs.img will make squashfs.img appear inside
+ initramfs at boot time.'''
+ # These exact names are required by dracut
+ squashname = "squashfs.img"
+ imgname = "LiveOS/rootfs.img"
+
+ # Create fs image of installtree
+ fsimage = joinpaths(self.workdir, "installtree.img")
+ open(fsimage, "wb").truncate(2*1024**3)
+ mountpoint = joinpaths(self.workdir, "rootfs")
+ os.mkdir(mountpoint, 0755)
+ logger.debug("formatting rootfs image: %s %s",
+ " ".join(self._mkfs), fsimage)
+ subprocess.check_call(self._mkfs + [fsimage], stdout=subprocess.PIPE)
+ logger.debug("mounting rootfs image at %s", mountpoint)
+ subprocess.check_call([self.lcmds.MOUNT, "-o", "loop",
+ fsimage, mountpoint])
+ try:
+ logger.info("copying installtree into rootfs image")
+ srcfiles = [joinpaths(self.root, f) for f in os.listdir(self.root)]
+ subprocess.check_call(["cp", "-a"] + srcfiles + [mountpoint])
+ finally:
+ logger.debug("unmounting rootfs image")
+ rc = subprocess.call([self.lcmds.UMOUNT, mountpoint])
+ if rc != 0:
+ logger.critical("umount %s failed (returncode %i)", mountpoint, rc)
+ sys.exit(rc)
+ os.rmdir(mountpoint)
+
+ # Make squashfs with rootfs image inside
+ logger.info("creating %s containing %s", squashname, imgname)
+ squashtree = joinpaths(self.workdir, "squashfs")
+ os.makedirs(joinpaths(squashtree, os.path.dirname(imgname)))
+ shutil.move(fsimage, joinpaths(squashtree, imgname))
+ squashimage = joinpaths(self.workdir, squashname)
+ subprocess.check_call([self.lcmds.MKSQUASHFS, squashtree, squashimage,
+ "-comp", compression])
+ shutil.rmtree(squashtree)
+
+ # Put squashimage in a new cpio image with dracut config
+ logger.debug("creating cpio image containing %s", squashname)
+ initramfsdir = joinpaths(self.workdir, "initramfs")
+ squash_cpio = joinpaths(self.workdir, "squashfs.cpio")
+ cmdline = joinpaths(initramfsdir, "etc/cmdline")
+ os.makedirs(os.path.dirname(cmdline))
+ # write boot cmdline for dracut
+ with open(cmdline, "wb") as fobj:
+ fobj.write("root=live:/{0}\n".format(squashname))
+ if self.style == "btrsquash":
+ fobj.write("rootflags=compress\n")
+ # add squashimage
+ shutil.move(squashimage, initramfsdir)
+ # create cpio container
+ chdir = lambda: os.chdir(initramfsdir)
+ find = subprocess.Popen([self.lcmds.FIND, "."], stdout=subprocess.PIPE,
+ preexec_fn=chdir)
+ cpio = subprocess.Popen([self.lcmds.CPIO, "--quiet", "-c", "-o"],
+ stdin=find.stdout,
+ stdout=open(squash_cpio, "wb"),
+ preexec_fn=chdir)
+ cpio.communicate()
+ shutil.rmtree(initramfsdir)
+
+ # create final image
+ logger.debug("concatenating initramfs.img and squashfs cpio")
+ logger.debug("initramfs.img size = %i", os.stat(self.initramfs).st_size)
+ with open(initrd.fpath, "wb") as output:
+ with open(self.initramfs, "rb") as fobj:
+ output.write(fobj.read())
+ with open(squash_cpio, "rb") as fobj:
+ output.write(fobj.read())
+ os.remove(self.initramfs)
+ os.remove(squash_cpio)
+
+ return True
@property
def kernels(self):
--
1.7.4
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