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43 lines
1.8 KiB
Plaintext
43 lines
1.8 KiB
Plaintext
pg_resetxlog is a program to clear the WAL transaction log (stored in
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$PGDATA/pg_xlog/), replacing whatever had been in it with just a dummy
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shutdown-checkpoint record. It also regenerates the pg_control file
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if necessary.
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THIS PROGRAM WILL DESTROY VALUABLE LOG DATA!!! Don't run it unless you
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really need it!!!
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pg_resetxlog is primarily intended for disaster recovery --- that is,
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if your pg_control and/or xlog are hosed badly enough that Postgres refuses
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to start up, this program will get you past that problem and let you get to
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your data files. But realize that without the xlog, your data files may be
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corrupt due to partially-applied transactions, incomplete index-file
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updates, etc. You should dump your data, check it for accuracy, then initdb
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and reload.
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A secondary purpose is to cope with xlog format changes without requiring
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initdb. To use pg_resetxlog for this purpose, just be sure that you have
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cleanly shut down your old postmaster (if you're not sure, see the contrib
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module pg_controldata and run it to be sure the DB state is SHUTDOWN).
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Then run pg_resetxlog, and finally install and start the new version of
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the database software.
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A tertiary purpose is its use by pg_upgrade to set the next transaction
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id and checkpoint location in pg_control.
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To run the program, make sure your postmaster is not running, then
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(as the Postgres admin user) do
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pg_resetxlog $PGDATA
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As a safety measure, the target data directory must be specified on the
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command line, it cannot be defaulted.
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If pg_resetxlog complains that it can't reconstruct valid data for pg_control,
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you can force it to invent plausible data values with
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pg_resetxlog -f $PGDATA
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If this turns out to be necessary then you *definitely* should plan on
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immediate dump, initdb, reload --- any modifications you do to the database
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after "pg_resetxlog -f" would be likely to corrupt things even worse.
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