Today I got a strange error during the execution of errpt command: "logopen: open: No such file or directory". At first I was scratching my head a bit, but in fact it is not hard at all.

This is due to missing the needed errlog file which should be located in /var/adm/ras/. All you have to do is to recreate it.
Please read on if you do not know how.

The error:

root@aix~# errpt
logopen: open: No such file or directory

WRONG solution:

root@aix~# [color=red]touch /var/adm/ras/errlog[/color]
root@aix~# errpt
logread: unexpected end of file
Unable to process the error log file /var/adm/ras/errlog.
root@aix~# rm /var/adm/ras/errlog

GOOD solution (will recreate a new 1MB errorlog file in [u]/var/adm/ras[u]):

root@aix~# [color=green]/usr/lib/errdemon -s 1048576[/color]
root@aix~# ls -la /var/adm/ras/errlog                      
-rw-rw-r--    1 root     system         8192 Feb  8 15:50 /var/adm/ras/errlog
root@aix~# errpt
IDENTIFIER TIMESTAMP  T C RESOURCE_NAME  DESCRIPTION
9DBCFDEE   0208155012 T O errdemon       ERROR LOGGING TURNED ON