pg_controldata \

pg_resetxlog \

ipc_check -

Simple test script to help in configuring IPC.

FreeBSD only, for now.

Dump contents of pg_control (database master file)

pg_resetxlog -

Reset the WAL log (pg_xlog) to recover from crash or format change

by Tom Lane <[email protected]>

subdir = contrib/pg_resetxlog

top_builddir = ../..

include $(top_builddir)/src/Makefile.global

OBJS = pg_resetxlog.o pg_crc.o

all: pg_resetxlog

pg_resetxlog: $(OBJS)

$(CC) $(CFLAGS) $(OBJS) $(LDFLAGS) $(LIBS) -o $@

pg_crc.c: $(top_builddir)/src/backend/utils/hash/pg_crc.c

rm -f $@ && $(LN_S) $< .

install: all installdirs

$(INSTALL_PROGRAM) pg_resetxlog$(X) $(bindir)

$(INSTALL_DATA) README.pg_resetxlog $(docdir)/contrib

installdirs:

$(mkinstalldirs) $(bindir) $(docdir)/contrib

uninstall:

rm -f $(bindir)/pg_resetxlog$(X) $(docdir)/contrib/README.pg_resetxlog

clean distclean maintainer-clean:

rm -f pg_resetxlog$(X) $(OBJS) pg_crc.c

depend dep:

$(CC) -MM -MG $(CFLAGS) *.c > depend

ifeq (depend,$(wildcard depend))

include depend

pg_resetxlog is a program to clear the WAL transaction log (stored in

$PGDATA/pg_xlog/), replacing whatever had been in it with just a dummy

shutdown-checkpoint record. It also regenerates the pg_control file

if necessary.

THIS PROGRAM WILL DESTROY VALUABLE LOG DATA!!! Don't run it unless you

really need it!!!

pg_resetxlog is primarily intended for disaster recovery --- that is,

if your pg_control and/or xlog are hosed badly enough that Postgres refuses

to start up, this program will get you past that problem and let you get to

your data files. But realize that without the xlog, your data files may be

corrupt due to partially-applied transactions, incomplete index-file

updates, etc. You should dump your data, check it for accuracy, then initdb

and reload.

A secondary purpose is to cope with xlog format changes without requiring

initdb. To use pg_resetxlog for this purpose, just be sure that you have

cleanly shut down your old postmaster (if you're not sure, see the contrib

module pg_controldata and run it to be sure the DB state is SHUTDOWN).

Then run pg_resetxlog, and finally install and start the new version of

the database software.

To run the program, make sure your postmaster is not running, then

(as the Postgres admin user) do

pg_resetxlog $PGDATA

As a safety measure, the target data directory must be specified on the

command line, it cannot be defaulted.

If pg_resetxlog complains that it can't reconstruct valid data for pg_control,

you can force it to invent plausible data values with

pg_resetxlog -f $PGDATA

If this turns out to be necessary then you *definitely* should plan on

immediate dump, initdb, reload --- any modifications you do to the database

after "pg_resetxlog -f" would be likely to corrupt things even worse.