I had another look at setting up a root file system on a btrfs subvolume
now that vmdebootstrap support grub, and freshed up the patch to give it
another go.
Unfortunately, grub is not able to find / when it is a btrfs subvolume:
# vmdebootstrap --roottype btrfs --image=test.img --verbose --grub
--bootsize=256M
Creating disk image
Creating partitions
Creating filesystem btrfs
Mounting /dev/mapper/loop0p2 on /tmp/tmpAtr8MZ
Creating filesystem ext2
Mounting /dev/mapper/loop0p1 on /tmp/tmpAtr8MZ/@/boot/
Debootstrapping
Give root an empty password
Removing udev persistent cd and net rules
Setting up networking
Updating the initramfs
Configuring grub2
command failed: ['chroot', '/tmp/tmpAtr8MZ/@', 'update-grub']
/usr/sbin/grub-probe: error: cannot find a device for / (is /dev mounted?).
Failed. Is grub2-common installed? Using extlinux.
Installing extlinux
Cleaning up
#
The resulting image were not able to boot.
This is the patch I used:
--- vmdebootstrap.orig 2014-10-18 20:35:19.000000000 +0200
+++ vmdebootstrap 2014-11-01 21:40:56.046766661 +0100
@@ -39,6 +39,9 @@
self.settings.boolean(['verbose'], 'report what is going on')
self.settings.string(['image'], 'put created disk image in FILE',
metavar='FILE')
+ self.settings.string(['roottype'],
+ 'specify file system type for /',
+ default='ext4')
self.settings.bytesize(['size'],
'create a disk image of size SIZE (%default)',
metavar='SIZE',
@@ -129,7 +132,7 @@
try:
rootdev = None
- roottype = 'ext4'
+ roottype = self.settings['roottype']
bootdev = None
boottype = None
rootdir = None
@@ -141,6 +144,15 @@
(rootdev, bootdev) = self.setup_kpartx()
self.mkfs(rootdev, type=roottype)
rootdir = self.mount(rootdev)
+ rootfsdir = rootdir
+ if 'btrfs' == roottype:
+ self.settings['package'].append("btrfs-tools")
+ # Put root in a subvolume, to ease snapshots and volume
management
+ newrootdir = "%s/@" % rootdir
+ self.runcmd(['btrfs', 'subvolume', 'create', newrootdir])
+ self.runcmd(['btrfs', 'subvolume', 'set-default', '@',
rootdir])
+ os.mkdir("%s/btrfs" % newrootdir)
+ rootdir = newrootdir
if bootdev:
if self.settings['boottype']:
boottype = self.settings['boottype']
@@ -168,9 +180,9 @@
if self.settings['image']:
if self.settings['grub']:
- self.install_grub2(rootdev, rootdir)
+ self.install_grub2(rootdev, rootdir, rootfsdir)
elif self.settings['extlinux']:
- self.install_extlinux(rootdev, rootdir)
+ self.install_extlinux(rootdev, rootdir, rootfsdir)
self.append_serial_console(rootdir)
self.optimize_image(rootdir)
if self.settings['squash']:
@@ -379,7 +391,12 @@
fstab = os.path.join(rootdir, 'etc', 'fstab')
with open(fstab, 'w') as f:
f.write('proc /proc proc defaults 0 0\n')
- f.write('%s / %s errors=remount-ro 0 1\n' % (rootdevstr, roottype))
+ if 'btrfs' == roottype:
+# f.write('%s / %s defaults 0 1\n' % (rootdevstr, roottype))
+ f.write('%s / %s subvol=@ 0 1\n' % (rootdevstr, roottype))
+ f.write('%s /btrfs %s defaults 1\n' % (rootdevstr, roottype))
+ else:
+ f.write('%s / %s errors=remount-ro 0 1\n' % (rootdevstr,
roottype))
if bootdevstr:
f.write('%s /boot %s errors=remount-ro 0 2\n' % (bootdevstr,
boottype))
@@ -472,7 +489,8 @@
with open(inittab, 'a') as f:
f.write('\nS0:23:respawn:%s\n' % serial_command)
- def install_grub2(self, rootdev, rootdir):
+ def install_grub2(self, rootdev, rootdir, rootfsdir):
+ # FIXME use rootfsdir
self.message("Configuring grub2")
# rely on kpartx using consistent naming to map loop0p1 to loop0
install_dev = os.path.join('/dev', os.path.basename(rootdev)[:-2])
@@ -486,13 +504,14 @@
self.runcmd(['chroot', rootdir, 'update-grub'])
self.runcmd(['chroot', rootdir, 'grub-install', install_dev])
except cliapp.AppException as e:
+ self.message(str(e))
self.message("Failed. Is grub2-common installed? Using extlinux.")
self.runcmd(['umount', os.path.join(rootdir, 'sys')])
self.runcmd(['umount', os.path.join(rootdir, 'proc')])
self.runcmd(['umount', os.path.join(rootdir, 'dev')])
- self.install_extlinux(rootdev, rootdir)
+ self.install_extlinux(rootdev, rootdir, rootfsdir)
- def install_extlinux(self, rootdev, rootdir):
+ def install_extlinux(self, rootdev, rootdir, rootfsdir):
if not os.path.exists("/usr/bin/extlinux"):
self.message("extlinux not installed, skipping.")
return
@@ -519,7 +538,7 @@
'-s', 'UUID', rootdev])
uuid = out.splitlines()[0].strip()
- conf = os.path.join(rootdir, 'extlinux.conf')
+ conf = os.path.join(rootfsdir, 'extlinux.conf')
logging.debug('configure extlinux %s' % conf)
f = open(conf, 'w')
f.write('''
@@ -528,7 +547,7 @@
label linux
kernel %(kernel)s
-append initrd=%(initrd)s root=UUID=%(uuid)s ro %(kserial)s
+append initrd=%(initrd)s root=UUID=%(uuid)s ro %(kserial)s %(rootflags)s
%(extserial)s
''' % {
'kernel': kernel_image,
@@ -536,11 +555,12 @@
'uuid': uuid,
'kserial':
'console=ttyS0,115200' if self.settings['serial-console'] else '',
+ 'rootflags': 'rootfsflags=subvol=@' if 'btrfs' ==
self.settings['roottype'] else '',
'extserial': 'serial 0 115200' if self.settings['serial-console']
else '',
})
f.close()
- self.runcmd(['extlinux', '--install', rootdir])
+ self.runcmd(['extlinux', '--install', rootfsdir])
self.runcmd(['sync'])
time.sleep(2)
--
Happy hacking
Petter Reinholdtsen
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