# ZFS: unsupported compression algorithm gzip-6



## scolyo (Apr 20, 2017)

Hi all,

I'm on a FreeBSD 10, with ZFS on Root. I've done a freebsd-update(8) fetch and install, with no problems. But when I try to reboot, I've the following messages:

```
ZFS: unsupported compression algorithm gzip-6
ZFS: i/o error - all block copies unavailable
don't know how to load module '/boot/kernel/kernel'
Error while including /boot/menu.rc, in the line:
menu-display
```
Google won't help me, I've just find this:

https://lists.freebsd.org/pipermail/freebsd-fs/2010-December/010306.html

So I've boot on a FreeBSD 10.3 live cd, import my zfs pool and set compression=off, but this don't work.

Any help would be welcome
Thanks in advance 

PS: Sorry for my bad English ;-)


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## usdmatt (Apr 20, 2017)

I would boot off the 10.3 CD and rewrite the boot partitions on the disk. If they're GPT partitioned you would normally run the following -


```
gpart bootcode -b /path/to/cd/boot/pmbr -p /path/to/cd/boot/gptzfsboot -i 1 adaX
```


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## SirDice (Apr 20, 2017)

Changing compression to off won't magically uncompress existing files. Those will still be compressed. Changing that setting only affects _new_ files.


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## scolyo (Apr 20, 2017)

usdmatt said:


> I would boot off the 10.3 CD and rewrite the boot partitions on the disk. If they're GPT partitioned you would normally run the following -
> 
> 
> ```
> ...



Thanks usdmatt, I've tied, but that's don't solve the problem.


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## scolyo (Apr 20, 2017)

SirDice said:


> Changing compression to off won't magically uncompress existing files. Those will still be compressed. Changing that setting only affects _new_ files.



Thanks SirDice, I've understand this after posting, the compressratio haven't move. Is there a way to force it?


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## scolyo (Apr 20, 2017)

Solved:
Boot off 10.3 CD
zpool import -fR /mnt zroot
cd /mnt
mv boot boot.bak
cp -R boot.bak boot
reboot

Works like a charm, sorry for the noise

Thanks again


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## SirDice (Apr 20, 2017)

scolyo said:


> I've understand this after posting, the compressratio haven't move. Is there a way to force it?


No. The only way to uncompress those files is to read the files and write them again. The write action will use the new setting.


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