$ pg_ctl -D /data start
postmaster successfully started

$ LOG:  database system shutdown was interrupted at  2003 - 04 - 15   20 : 59 : 10  GMT
LOG:  open of /data/pg_xlog/ 0000000000000000  (log file  0 , segment  0 ) failed: No
such file or directory
LOG:  invalid primary checkpoint record
LOG:  open of /data/pg_xlog/ 0000000000000000  (log file  0 , segment  0 ) failed: No
such file or directory
LOG:  invalid secondary checkpoint record
PANIC:  unable to locate a valid checkpoint record
LOG:  startup process (pid  1488 ) was terminated by signal  6 
LOG:  aborting startup due to startup process failure

$ ls /data/pg_xlog/
 0000000000000006 

$ ls /data/pg_clog/
 0000 

pg_resetxlog -o25322 -x1406 -l0000000000000006, 0000  /data
Transaction log reset

$ pg_ctl -D /data start
postmaster successfully started

$ IpcSemaphoreCreate: semget(key= 5432084 , num= 17 ,  03600 ) failed: No space left o
n device

This error does *not* mean that you have run out of disk space.

It occurs when either the system limit for the maximum number of
semaphore sets (SEMMNI), or the system wide maximum number of
semaphores (SEMMNS), would be exceeded.  You need to raise the
respective kernel parameter.  Alternatively, reduce PostgreSQL's
consumption of semaphores by reducing its max_connections parameter
(currently 32).

The PostgreSQL Administrator's Guide contains more information about
configuring your system for PostgreSQL.