# [SOLVED]mount: unknown filesystem type 'btrfs'

## SwallowUnladen

Hi,

I am a newbie. I wont to make btrfs my root, but for now I am working from ext4. I was learning a thing or two about gentoo, but this one totally escapes me:

```
# mount  /dev/sda8 /mnt/btrfsroot/

mount: unknown filesystem type 'btrfs'

```

You have to recompile kernel without using genkernel! God that was obvious. Trust no one!

Answer was here.

Fixed the link, there was an extraneous ] after the =. -- desultoryLast edited by SwallowUnladen on Tue Aug 04, 2015 7:35 pm; edited 2 times in total

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## Keruskerfuerst

If you can´t mount a btrfs filesystem, the kernel does not include the support.

Can you try the following mount command:

mount  -t btrfs /dev/sda8 /mnt/btrfsroot/

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## SwallowUnladen

 *Keruskerfuerst wrote:*   

> If you can´t mount a btrfs filesystem, the kernel does not include the support.
> 
> Can you try the following mount command:
> 
> mount  -t btrfs /dev/sda8 /mnt/btrfsroot/

 

The output was the same. You are right and solutions was as expected in kernel.

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## davidm

Yes.  Make sure you are booting from the kernel you think you are.  It's a common mistake or to forget to reboot to actually run that kernel.  :Smile: 

'uname -a'

'cat /proc/filesystems'

'lsmod | grep btrfs'

'ls -l /boot/config-$(uname -r)'

grep -i btrfs `ls /boot/config-$(uname -r)` (note use of backtics not single quotes)

Also maybe see what 'btrfs device scan' does and tell us a bit more about your setup such as your kernel, how many disks (sngle or multi-device) your btrfs array is and maybe 'fdisk -l' output if still stuck along with an explanation of what each partition is supposed to be.

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## SwallowUnladen

 *davidm wrote:*   

> Yes.  Make sure you are booting from the kernel you think you are.  It's a common mistake or to forget to reboot to actually run that kernel. 
> 
> 'uname -a'
> 
> 'cat /proc/filesystems'
> ...

 

I probably did a ton of this human mistakes today, it seams my main problem with gentoo is human factor.

Also about 'ls -l /boot/config-$(uname -r)'. Where does this file comes from. I am only half(or less) of my way through handbook so maybe I will find answer later.

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## Keruskerfuerst

/boot/config-$(uname -r)

takes the latest kernel config.

uname -a gives the output of the used kernel and basic system information.

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## SwallowUnladen

 *Keruskerfuerst wrote:*   

> /boot/config-$(uname -r)
> 
> takes the latest kernel config.
> 
> uname -a gives the output of the used kernel and basic system information.

 

This is what I have:

```

efi                                      intel-ucode.img                       refind_linux.conf                         vmlinuz-kernel-genkernel-x86_64-4.0.5-gentoo

initramfs-genkernel-x86_64-4.0.5-gentoo  kernel-genkernel-x86_64-4.0.5-gentoo  System.map-genkernel-x86_64-4.0.5-gentoo

```

So I supose this config-$(uname -r), comes from:

```
# cp /usr/src/linux/.config /boot/config-$(uname -r)
```

Right?

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## Keruskerfuerst

You should habve a look at the bash reference here: http://www.gnu.org/software/bash/

cp means copy. See also info cp on console.

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