# How to install grub2 on FreeBSD



## Yampress (Dec 20, 2011)

How to install grub2, which may be useful to run multiple systems described below. Of course, previously tested by me like everyone my faq.


THE WORKS
* All I do the following as root. *
Install grub 2 first. I do it with packages


```
pkg_add-r grub2
```

Prepares the directory structure

```
cd /boot
mkdir grub
cd grub
touch grub.cfg
```

For grub.cfg adds the following entry

```
set timeout = 3
set default = "0"
menuentry "FreeBSD 8 Server" {
insmod ufs2
     set root = (hd0, 1)
chainloader 1
}
```


```
set root = (hd0, 1)
```
This is for disk 1, and freebsd FreeBSD installed on the first slice.


```
set root = (hd0, 3)
```
This is for disk 1, and freebsd installed on the third slice.
And just for themselves similarly change the parameters ...

Now copies the files to the right place to /boot/grub


```
cp-Rf /usr/local/lib/grub/i386-pc /boot/grub
```

Before you install grub in the MBR disk must be allowed to overwrite the MBR freebsd FreeBSD
If we do not, freebsd FreeBSD will not be able to install grub in the MBR.

```
sysctl kern.geom.debugflags = 16
```
And that's it. It remains to install grub

```
grub-install /dev/ad0
```

If a message pops up like this, everything is ok

```
freebsdserver # grub-install /dev/ad0
Installation finished. No error reported.
freebsdserver #
```

After installation, it looks like this





Now you can add other systems. windows, linux and bsd other configuration file.


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## wblock@ (Dec 20, 2011)

Yampress said:
			
		

> Before you install grub in the MBR disk must be allowed to overwrite the MBR freebsd FreeBSD
> If we do not, freebsd FreeBSD will not be able to install grub in the MBR.
> 
> ```
> ...



That setting actually allows writes to areas of the disk that are in use by geom.  Typically that's for the very special case of writing to an important block of a mounted partition.  The MBR should not need that, and in fact it should be very rare to need that sysctl at all.

(Some of the misunderstanding is my fault, since I didn't understand it and promoted the misuse in a couple of articles.  Sorry about that.)


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