Re: [gentoo-user] Clone live system as a simple backup?

[YoYo Siska]

On Wed, Mar 07, 2012 at 02:47:08PM -0500, Joshua Murphy wrote:
> On Wed, Mar 7, 2012 at 8:55 AM,  <gandalf@××××××××××.uk> wrote:
> >> Hi,
> >>    I'm interested in the idea of cloning a live, complicated hardware
> >> system onto a single external hard drive as a simple backup. I would
> >> like this external drive to be completely bootable. What's the best
> >> way to approach doing this? I was considering just doing a Gentoo
> >> install from scratch but figured maybe there's a way to clone enough
> >> of the live system to get me there less painfully?
> >>
> >>    The system I'm playing with has five 500MB hard drives with most
> >> partitions in linked together in various forms of RAID. (1, 5 & 6)
> >> That said, the total storage that this system presents KDE and the
> >> users is about 600GB.
> >>
> >>    I have an external 1TB eSATA drive which is therefore large enough
> >> to hold everything on this system, albeit without the reliability of
> >> RAID which is fine for this purpose.
> >>
> >>    The system looks more or less like:
> >>
> >> /dev/sda1 -> /boot (50MB)
> >> /dev/sdb1 -> /boot copy
> >> /dev/sdc1 -> /boot copy
> >>
> >> c2stable ~ # df
> >> Filesystem     1K-blocks      Used Available Use% Mounted on
> >> rootfs          51612920  31862844  17128276  66% /
> >> /dev/root       51612920  31862844  17128276  66% /
> >> rc-svcdir           1024        92       932   9% /lib64/rc/init.d
> >> udev               10240       476      9764   5% /dev
> >> shm              6151284         0   6151284   0% /dev/shm
> >> /dev/md7       389183252 350247628  19166232  95% /VirtualMachines
> >> tmpfs            8388608         0   8388608   0% /var/tmp/portage
> >> /dev/sda1          54416     29516     22091  58% /boot
> >> c2stable ~ # cat /proc/mdstat
> >> Personalities : [linear] [raid0] [raid1] [raid10] [raid6] [raid5]
> >> [raid4]
> >> md6 : active raid5 sdb6[1] sdc6[2] sda6[0]
> >>       494833664 blocks super 1.1 level 5, 64k chunk, algorithm 2 [3/3]
> >> [UUU]
> >>
> >> md7 : active raid6 sdb7[1] sdc7[2] sda7[0] sdd2[3] sde2[4]
> >>       395387904 blocks super 1.2 level 6, 16k chunk, algorithm 2 [5/5]
> >> [UUUUU]
> >>
> >> md3 : active raid6 sdb3[1] sdc3[2] sda3[0] sdd3[3] sde3[4]
> >>       157305168 blocks super 1.2 level 6, 16k chunk, algorithm 2 [5/5]
> >> [UUUUU]
> >>
> >> md126 : active raid1 sdc5[2] sda5[0] sdb5[1]
> >>       52436032 blocks [3/3] [UUU]
> >>
> >> unused devices: <none>
> >> c2stable ~ #
> >>
> >>    /dev/md3 is a second Gentoo installation that doesn't need to be
> >> backed up at this time. md6 is an internal RAID used to back up md7
> >> daily. It doesn't need to be backed up, but if the machine totally
> >> failed killing all the drives that wouldn't survive so currently I
> >> back up md126 to md6 daily, and then back up md6 weekly to an external
> >> eSATA drive.
> >>
> >>    What I'd like to do is clone
> >>
> >> 1) /boot (sda1) including grub and everything required to make it bootable
> >> 2) back up the system portions of dev/md126 (/ )
> >> 3) Add some swap space on the external drive
> >> 4) back up /dev/md7 which is all of my VMs
> >> 5) back up /home to a separate partition on the external drive
> >> 6) back up some special things like /var/lib/portage/world and
> >> /usr/portage/packages
> >>
> >> My thought is that this drive is basically bootable, but over time
> >> gets out-of-sync with the system. However should the system fail I've
> >> got a bootable external drive with all the binary packages required to
> >> get it running again quickly. However I can always boot the drive, do
> >> an emerge -ek @world, and basically be back to where I am as of the
> >> last backup.
> >>
> >> The external drive will look something like:
> >>
> >> /dev/sdg1 -> /boot
> >> /dev/sdg2 -> swap
> >> /dev/sdg3 -> / (not including /home, /usr/portage/distfiles, etc)
> >> /dev/sdg5 -> /usr/portage/packages
> >> /dev/sdg6 -> /dev/md7
> >>
> >> etc....
> >>
> >>    I will of course have to modify grub.conf and /etc/fstab to work
> >> from this drive but that's no big deal.
> >>
> >>    What are folks best ideas about how to approach doing something like
> >> this?
> >>
> >> Thanks,
> >> Mark
> >>
> >>
> > Hi,
> >    Why don't you something like bind mount the folders you want to copy
> > and rsync them to the eSATA disk, after creating a similar partition
> > layout on it. Remember to exclude system files like /proc/*, /dev/*
> > and /sys/* as well as the ones you want to exclude yourself from the
> > rsync. When you want to sync the clone again just do the same again
> > and rsync the changes.
> >
> > Regards,
> > Derek
> >
> >
>
> As an added note on this, rsync's --one-file-system (-x) flag is handy
> for avoiding grabbing unneeded things, but will typically leave you
> without the base few device nodes needed to boot the backup, those can
> either be grabbed from a stage3, or created with (courtesy of Linux
> From Scratch's section "6.2.1. Creating Initial Device Nodes"):
>
> mknod -m 600 ${backup}/dev/console c 5 1
> mknod -m 666 ${backup}/dev/null c 1 3

The best way to copy a filesystem without any sub-mounts is to
mount-bind it to some directory and copy it from there:

mkdir /tmp/root
mount --bind / /tmp/root
rsync -a /tmp/root/ /mnt/backup/

Note that copying a rw filesystem (especially /) on a running system
isn't a very clean operation..

yoyo