Ubuntu System Restore

Sun Oct 30 20:40:19 UTC 2011

You need to either have a local repository or download from the internet
again. I've used 'apt-mirror' in the past to maintain a local cache but
that was when I was building local systems with a minimal Debian installer.
I don't even know if the standard Ubuntu installer can load off a local
cache. (I guess the process is to do the install "without updates", change
your sources.list files, then upgrade from the cache.)

It's also worth remembering that the specific versions of your packages may
not be available when you need to restore your system. This is usually a
good thing since more recent versions have a shot at preventing whatever
caused you to lose your system in the first place (e.g., closing
vulnerabilities) but some people may need to restore the system exactly.

On checksums - I checked my system and almost none of the conffiles have
checksums. (In fact that may be against packaging standards - I would have
to check.) That's a bummer since it means that there's no easy way of
seeing what's changed unless you peek into the .deb file. There are some
deb tools that can do this but since I can do it programmatically I usually
just did that.

The 'monster diff' is just a comment on the number of files involved. What
I actually did create two lists, one generated by walking the filesystem
and the other generated by concatenating all of the *.files and *.md5sums
metadata and then comparing them. I did this programmatically but you could
also create actual files, sort them, and then run a diff on them. IIRC I
typically had over 70k files.

On Fri, Oct 28, 2011 at 3:33 AM, Gaurav Saxena <grvsaxena419 at gmail.com>wrote:

> Hello all
>
> On Fri, Oct 7, 2011 at 4:45 AM, Bear Giles <bgiles at coyotesong.com> wrote:
>
>> I've written a few prototypes and this comes down to four issues. Some of
>> the details below are debian/ubuntu-specific but the same concepts will
>> apply to redhat.
>>
>> 1. User data (/home) must be backed up explicitly. (ditto server data on
>> servers).
>>
>> 2. Packages should NOT be backed up. All you need is the package name and
>> version. Reinstall from .deb and .rpm if necessary since this way you're
>> sure that you never restore compromised files.
>>
> But it might be possible that the package files are not available on the
> system. That means for all the packages installed the .deb files need to be
> downloaded from the internet for restore purpose ?
>
>
>> 3. Configuration data (/etc) must be backed up explicitly. This is tricky
>> because backing up the entire directory will cause its own problems. Worse,
>> some applications keep their configuration files elsewhere. The best
>> solution I've found is to scan the package metadata to identify
>> configuration files and to only save those with a different checksum than
>> the standard file.
>>
> Ok. Nice idea indeed , but is there checksum associated with the files in
> the package ? Or that can be calculated at the time of restore ? What you
> say ?
>
>
>>
>> 4. Local files. Ideally everyone would keep these files under /usr/local
>> and /opt but that's rarely the case. The best solution I've found is to
>> scan the debian package metadata and do a monster diff between what's on
>> the filesystem under /bin, /sbin, /usr and (chunks of) /var with what's in
>> the metadata.
>>
> Could you suggest me some way of scanning the debian package metadata
> without actually downloading the packages? and how to this monster diff ?
>
>>
>> It's worth noting that the last item isn't that hard if you have a strict
>> security policy that everything under those directories MUST be in a
>> package. It's deleted without a second thought if it's not. You can still
>> do everything you could before, you just need to create a local package for
>> it.
>>
>> So what do you do with this? The best solution, which I haven't
>> implemented yet, is to handle #2 and #3 with autogenerated packages. You
>> set up one or more local packages that will install the right software and
>> then overwrite the configuration files. You can fit everything, including
>> original package archive, on a single DVD.
>>
> Could you please tell some detail about autogenerated packages ? Like if
> we have a list of packages installed on the system, We need to reinstall
> those all softwares  and remove those which are installed after the restore
> point?
>
>>
>> BTW Debian has a C++ interface to the package metadata. I've never used
>> it - I find it easier to just scan the metadata directory myself. There's
>> also hooks that will allow your application to be called at each step
>> during a package installation or removal. You could, in theory, keep your
>> snapshots current to the last minute that way.
>>
> So whenever a package is installed or removed I will update my backup
> according to that ? By reading package metadata determine which files are
> changed by that package and update those files in the backup ?
>
>>
>>
>> On Fri, Sep 30, 2011 at 12:01 AM, Gaurav Saxena <grvsaxena419 at gmail.com>wrote:
>>
>>> Hello Aaron
>>> Thanks a lot for your quick reply.
>>>
>>> On Fri, Sep 30, 2011 at 10:03 AM, Aaron C. de Bruyn <aaron at heyaaron.com>wrote:
>>>
>>>> In Windows, the ability to snapshot is built into the filesystem.
>>>> In Linux, you must be running a filesystem that supports snapshots.  I
>>>> know LVM supports snapshotting and I believe BRTFS has support, but
>>>> other than that I'm not sure.
>>>>
>>>> Yes I read the logic behind windows system restore. But I think we can
>>> take some other approach for this, that will be better as all users won't
>>> be able to spare an extra partition formatted brtfs.
>>>
>>>
>>>> Basically, your program would have to check the file system that is
>>>> used on the computer (remember Linux can have many types of file
>>>> systems mounted at the same time), then (in the case of LVM) make sure
>>>> there's enough free space to snapshot, and finally take the snapshot.
>>>>
>>>> Ok. Do I have to snapshot the whole system partition / important system
>>> files to the brtfs partition ?
>>>
>>>
>>>> When the snapshots start filling up, you would either need to delete
>>>> them or detect the low space and resize them.
>>>>
>>>> In my personal opinion, snapshotting in Linux is currently a pain in
>>>> the rear.  It sounds like BTRFS could change that, but it's still a
>>>> ways off.
>>>>
>>>> Ok.  I will try another approach that will be better as suggested by
>>> people here.
>>>
>>>
>>>> -A
>>>>
>>>>
>>>> On Thu, Sep 29, 2011 at 21:00, Gaurav Saxena <grvsaxena419 at gmail.com>
>>>> wrote:
>>>> > Hello all,
>>>> > I want to write a windows system restore like program for ubuntu ,
>>>> which
>>>> > will have options for creating restore points for the system and then
>>>> > restoring it back to that point. Also I will as an extension provide
>>>> support
>>>> > for older version of a file as is in windows currently. I need your
>>>> help to
>>>> > find how to start with this in ubuntu. I know that I have to snapshot
>>>> the
>>>> > system when creating a restore point and then restore it. I need some
>>>> > starting pointers so that I can start doing this work. Also if this
>>>> has
>>>> > already been done please inform me. I got this idea from
>>>> >  https://wiki.ubuntu.com/SystemRestore.
>>>> > --
>>>> > Thanks and Regards ,
>>>> > Gaurav
>>>> >
>>>> > --
>>>> > Ubuntu-devel-discuss mailing list
>>>> > Ubuntu-devel-discuss at lists.ubuntu.com
>>>> > Modify settings or unsubscribe at:
>>>> > https://lists.ubuntu.com/mailman/listinfo/ubuntu-devel-discuss
>>>> >
>>>> >
>>>>
>>>
>>>
>>>
>>> --
>>> Thanks and Regards ,
>>> Gaurav
>>>
>>>
>>>
>>> --
>>> Thanks and Regards ,
>>> Gaurav
>>>
>>> --
>>> Ubuntu-devel-discuss mailing list
>>> Ubuntu-devel-discuss at lists.ubuntu.com
>>> Modify settings or unsubscribe at:
>>> https://lists.ubuntu.com/mailman/listinfo/ubuntu-devel-discuss
>>>
>>>
>>
>
>
> --
> Thanks and Regards ,
> Gaurav
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://lists.ubuntu.com/archives/ubuntu-devel-discuss/attachments/20111030/2e98a6a0/attachment.html>