Subject: Re: security sysctl? (was: r/o filesystem restrictions for firewall?)
To: Jon Lindgren <>
From: Allen Briggs <>
List: tech-kern
Date: 10/24/2000 15:01:25
On Tue, Oct 24, 2000 at 01:45:06PM -0400, Jon Lindgren wrote:
> Then I definitely don't know exactly what securelevel 2 is.  Is there a
> spot to read up on exactly what it does and what it affects?


     2     Highly secure mode - same as secure mode, plus disks are always
           read-only whether mounted or not, new disks may not be mounted, and
           existing mounts may only be downgraded from read-write to read-on-
           ly.  This level precludes tampering with filesystems by unmounting
           them, but also inhibits running newfs(8) while the system is multi-

           The settimeofday(2) system call can only advance the time.

           The state of ipf(8) (the in-kernel IP filtering facility) may not
           be changed.

           Downgrading from highly secure mode to insecure mode (that is, to
           single-user mode) always requires the root password to be entered
           on the console, whether the console is marked as 'secure' in
           /etc/ttys or not.