How To Clear /var/adm/wtmpx

On Solaris if /var/adm/wtmpx has got so big as to break the last command or fill up all your disk space, here's how to fix it:

This will create a new wtmpx file with only the last 100 entries in it.

# /usr/lib/acct/fwtmp < /var/adm/wtmpx | tail -100 > /tmp/wtmpx.ascii
# /usr/lib/acct/fwtmp -ic < /tmp/wtmpx.ascii > /var/adm/wtmpx
# rm /tmp/wtmpx.ascii

fwtmp parses the wtpmx file and dumps out the last 100 entries in ascii to a file.
Rerun fwtmp with the -ic params will read this file and create an equivalent binary wtmpx file to replace yours.

Note: If fwtmp is not available on your system you'll need to install the system accounting packages SUNWaccu & SUNWaccr.