Re: [ADMIN] Re: [SQL] Data recovery

Tom Lane wrote:

>
> Bob Kruger <bkruger@mindspring.com> writes:
> > I am recovering a system from a complete HD crash.
> > I have a backup of the Postgres data directory, e.g.
> > /usr/local/pgsql/data/base.
> > Is there a way or method to have Postgres pick these databases up again?
> > The version of Postgres run in this machine was/is 6.4.2.
>
> If you have a backup of the whole pgsql/data directory, just reinstall
> the same Postgres release, restore the data directory (instead of doing
> an initdb), and you should be in fat city.
>
> If you only have the data/base subdirectory, you will need to work
> harder; you'll have to regenerate the top-level files.  I think if you
> get pg_shadow and pg_database right you will be OK.  First, install and
> initdb to get a basic set of files.  You will need to recall the old set
> of users (including their userIDs) in order to reconstruct pg_shadow.
> After you've done the createusers, issue a createdb for each old
> database (subdirectory of base/) so that they have entries in
> pg_database.  Then, shut down the postmaster, blow away the contents of
> the base/ subdirectory and restore it from tape, and restart.  I think
> it'll work...
>
> In any case it's critical to install the same Postgres version you
> were using.

    NO  -  this  cannot  work.  He  surely  needs the entire data
    directory because the information in the heap's relies on the
    bits   in  data/pg_log.   And  that  info  (which  XID's  are
    committed and which not) cannot  be  reconstructed  from  the
    files - no chance.


Jan

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