I know what these files record, but I'd like to known what 'u','w','b' prefixes mean.
Can anyone shed some light?
The 'u' stands for user.
utmp gives information about who is on the system.
The 'w' in
wtmp probably comes from 'who'.
The 'b' comes from 'bad',
btmp records the bad login attempts.
The names are a bit cryptic, as so often on Unix/Linux.