in "restrictions" section of man adduser(8) still isn't reflected information for wtmp accounting db coming in 9.0-release. "You can change UT_NAMESIZE in <utmp.h> and recompile the world;" is actual for for FreeBSD <9.0. For FreeBSD 9.0+ correct way is: #define MAXLOGNAME 17 /* max login name length (incl. NUL) */ in /sys/sys/param.h