How to find calculated CRC checksum of pg_controldata

From: Matthew Rantala <mjrantal(at)umn(dot)edu>
To: pgsql-admin(at)postgresql(dot)org
Subject: How to find calculated CRC checksum of pg_controldata
Date: 2014-04-03 13:58:26
Message-ID: 533D6902.9080300@umn.edu
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Hello,

Question: Is there a way to obtain the calculated CRC checksum for
pg_controldata from the command line?

I'm asking this because we had our database get wiped out, and for a
variety of reasons, did not have a clean backup of the data directory. I
did, however, have a complete set of WAL files for the database from the
origin of the instance's life. I was able to use these to restore the
database into a new database that I engineered look like a copy of the
original by editing the pg_control file (and first log file) by changing
the Database system identifier and the CRC checksum.

Finding the correct CRC checksum, however, was a pain. I downloaded the
code and modified pg_controldata.exe so it would display the file CRC
and calculated checksums so I would know what the correct value was.

I'm in the process of documenting what I did and it would make the whole
process much easier if there is a way to determine the CRC checksum
without having to dig into the source code. I am currently using 9.2.6.

Thanks for any info,

Matt, who was extremely lucky that I initiated WAL logging at the very
beginning.

--

Matthew J Rantala, GISP
Minnesota Geological Survey
University of Minnesota
2642 University Ave.
St. Paul, MN 55114-1057
(612) 627-4780 x206

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