This has the following advantages:
- During boot, the BOOT_TIME record is now written right after the file
systems become writable, but before users are allowed to log in. This
means that they can't cause `hidden logins' by logging in right before
init(8) kicks in.
- The pututxline(3) function may potentially block on file locking,
though this is very rare to occur. By placing it in an rc script, the
user can still kill it with ^C if needed.
- Most importantly: jails don't use init(8). This means that a force
reboot of a system running jails will leave stale entries in the
accounting database of the jails individually.
