# Changing boot delay with boot0cfg



## ivanz (Sep 18, 2013)

Hello, 
I would like to speed up boot with the boot0cfg command (2 second delay), but I want to make sure not to break my MBR.

My /etc/fstab:

```
/dev/ada1p2	/		ufs	rw	1	1
/dev/ada1p3	none		swap	sw	0	0
pro             /proc           procfs  rw      0       0
```

Should I use the command `boot0cfg -t 2 /dev/ada1` or this one: `boot0cfg -t 2 /dev/ada1p2`?

Thank you for your help.


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## wblock@ (Sep 18, 2013)

Hold on.  You are not using an MBR disk, the "p" notation for partitions means it is GPT.  I don't know what will happen if boot0 is installed in the PMBR, probably nothing good.

Which delay are you trying to reduce?


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## kpa (Sep 18, 2013)

I think you can replace the MBR code in the PMBR with boot0 and use the minimal boot selector even with GPT disks. What the PMBR really does is cover the disk with an MBR partition of a special type so that disk utilities that understand only MBR partitioning won't stomp over GPT data structures. The PMBR boot loader code should be the same as /boot/boot that is used on an MBR partitioned disk.

The command to install the boot0 loader on /dev/ada1 is: `bootcfg -B /dev/ada1`

Test first on a non-critical system.


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## wblock@ (Sep 18, 2013)

I doubt that there's room in boot0 to handle GPT partitions in addition to MBR partitions.  It might not see GPT partitions and just be able to select different disks.  The first 446 bytes (boot code) in /boot/mbr and /boot/pmbr do differ, although maybe not in function.


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## kpa (Sep 18, 2013)

The boot0 loader won't see the GPT partitions obviously but if it works it will allow selection of boot from the first or the second disk of the system. Possible even selecting individual partitions from the second disk if that one is MBR partitioned.


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## ivanz (Sep 18, 2013)

wblock@ said:
			
		

> Hold on.  You are not using an MBR disk, the "p" notation for partitions means it is GPT.  I don't know what will happen if boot0 is installed in the PMBR, probably nothing good.
> 
> Which delay are you trying to reduce?


I want to reduce delay when the boot asks for:

```
F1 Other
F2 FreeBSD
```


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## SirDice (Sep 18, 2013)

Why not remove it completely? There's only one OS on the disk so having a boot selector is rather pointless. Besides that, I was under the impression that boot0cfg(8) shouldn't (can't?) be used on GPT disks.


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## wblock@ (Sep 18, 2013)

Agreed.  Use the BIOS disk boot menu instead, and restore the PMBR.  If the first disk does not have FreeBSD on it, use whatever tools that came with that operating system to fix it.  Back it up first.  If it does have FreeBSD but boot0 calls it "Other" because it does not recognize GPT, this should work to reinstall the PMBR (but back up first, because this has not been tested by itself for this purpose):
`# gpart bootcode -b /boot/pmbr`


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