Obtained from: Whistle Communications

control program to control the facility of the bootblocks
to fetch a default bootstring from a fixed location on the disk.

See the manpage for more info.

1 files changed, 87 insertions, 0 deletions

diff --git a/sbin/nextboot/nextboot.8 b/sbin/nextboot/nextboot.8
new file mode 100644
index 0000000..b301fba
--- /dev/null
+++ b/sbin/nextboot/nextboot.8
@@ -0,0 +1,87 @@
+.Dd July 9, 1996
+.Dt NEXTBOOT 8
+.\".Os BSD 4
+.Sh NAME
+.Nm nextboot
+.Nd Install a default bootstring block on the boot disk
+.Sh SYNOPSIS
+.Nm
+.Op Fl b
+.Ar filename bootstring ...
+.Pp
+.Nm
+.Op Fl e
+.Op Fl d
+.Ar filename
+.Bl -tag -width time
+.It Fl b
+Is used for bootstrapping (initially configuring) the nameblock. Without
+this, 
+.Nm
+will refuse to write to a block that does not already contain the magic
+number.
+.It Fl d
+temporarily disables an existing name block by changing a bit
+in the magic number.
+.It Fl e
+restores the good magic number on a block disabled by -d.
+.El
+.Sh PROLOGUE
+The FreeBSD program
+.Nm
+controls the actions of the boot blocks at the time of the next boot.
+If compiled with the correct option,
+the boot blocks will check the nameblock for a magic number and a 
+default name to use for booting. If compiled to do so they will also 
+delete the name from the block, ensuring that if the boot should fail,
+then it will not be tried again. It is the job of /etc/rc to use 
+.Nm
+to re-install the string if that boot is found to have succeeded.
+This allows a one-time only boot string to be used for such applications
+as remote debugging, and installation of new, untrusted kernels.
+The nameblock is defined at compile time to be the second physical block
+on the disk.
+.Pp
+.Sh DESCRIPTION
+.Nm
+first checks that the disk has an fdisk table and checks that none of the 
+partitions defined in that table include the nameblock. If the name block is 
+shown to be unused, it will install the bootstrings given as arguments,
+one after the other, each preceded by a small magic number, and NULL
+terminated. The end of the list of strings is delimited by a sequence of 
+0xff bytes. If the boot blocks are compiled to write back the nameblock
+after each boot, it will zero out the supplied names as it uses them,
+one per boot,
+until it reaches the 0xff, at which time it will revert to the compiled in
+boot string. At this time the nameblock will contain only zeroed out names.
+.Pp
+An example of usage might be:
+.Bd -literal
+   nextboot -b  /dev/rwd0 1:sd(0,a)/kernel.experimental wd(0,a)/kernel.old
+.Ed
+.Pp
+Which would instruct the boot blocks at the next boot,
+to try boot the experimental kernel off the scsi disk.
+If for any reason this failed, the next boot attempt would 
+boot the kernel
+.Em /kernel.old
+off the IDE drive.  (assuming the write-back option were enabled) If this
+in turn failed. the compiled in default would be used.
+.Pp
+If the write-back feature is disabled, the nextboot program is a convenient way
+to change the default boot string. Note, that should the file specified in
+the nameblock be non-existant, then the name compiled into the boot blocks
+will be used for the boot rather than the next name in the nameblock. The 
+nameblock is only consulted ONCE per boot.
+
+
+.Sh SEE ALSO
+.Xr boot 8
+.Xr disklabel 8
+.Xr fdisk 8
+.Sh BUGS
+The entire program should be made more user-friendly.
+.Pp
+Whether to write back or not should be specified at run-time in the nameblock
+so that the boot blocks need not be altered to get this feature.
+.Pp