Howto clean an AIX wtmp log file (/var/adm/wtmp)

This document explains how you can reduce the size of wtmp in a GOOD way
This info is valid for AIX 4.3.3, AIX 5.1, AIX 5.2 and AIX 5.3.

Cleaning of wtmp on AIX is not done by "echo >/var/adm/wtmp". There are 2 supported ways to clean wtmp:

• cp /dev/null /var/adm/wtmp
• format /var/adm/wtmp to ASCII text, clean the 'bogus' entrys and convert it back to wtmp format, you can do this by using the tool fwtmp:
  • be sure /tmp has enough space
  • convert the wtmp to ASCII --> /tmp/dummy.file
  • /usr/sbin/acct/fwtmp </var/adm/wtmp >/tmp/dummy.file
  • edit the file /tmp/dummy.file via "grep -v" or just plain vi
  • convert the ASCII output back -->/var/adm/wtmp
  • /usr/sbin/acct/fwtmp -ic <dummy.file >/var/adm/wtmp

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