Downgrade FreeBSD 5.1 or 5.2 -> 4.9

David Wolfskill david at
Thu Jan 22 11:44:01 PST 2004

>Date: Thu, 22 Jan 2004 11:33:10 -0800
>From: John Kennedy <jk at>
>To: freebsd-current at
>Subject: Re: Downgrade FreeBSD 5.1 or 5.2 -> 4.9
>Sender: owner-freebsd-current at

>  Will 4.x and 5.x play nice if they have a partition (slice?) in common?

They can (play nice), yes.

It helps to use UFS1 file systems.   :-}

>  For example, /home that was mounted by both a 4.x and 5.x depending on
>whatever was booted at the moment.  Probably have UFS issues, but I don't
>know if 5.x will "corrupt" a 4.x filesystem.

On my laptop, on which I have been tracking both -STABLE and -CURRENT
for quite a while, /home is a symlink (for each bootable /) to
/common/home.  Here is how things look while running -STABLE:

localhost(4.9-S)[1] df -k
Filesystem  1K-blocks    Used    Avail Capacity  Mounted on
/dev/ad0s1a    161262   47614   100748    32%    /
mfs:24         515606      16   474342     0%    /tmp
/dev/ad0s1e   1902528 1084144   666182    62%    /usr
/dev/ad0s2a    161262   77676    70686    52%    /S2
/dev/ad0s2e   1902528 1016476   733850    58%    /S2/usr
/dev/ad0s3a    161262   78218    70144    53%    /S3
/dev/ad0s3e   1899102 1014676   732498    58%    /S3/usr
/dev/ad0s3f   1016303   26938   908061     3%    /var
/dev/ad0s3g  10163268 8736126   614081    93%    /common
/dev/ad0s3h  16531530  994612 14214396     7%    /bkp
procfs              4       4        0   100%    /proc

While running -CURRENT, I boot from ad0s3a, and I don't mount anything
(by default) from slice 1 or 2.  ad0s3f gets mounted on /var, ad0s3g
gets mounted on /common, and ad0s3b is used as swap (with a swap-backed
/tmp) in all cases.

>  I downgraded via reinstall once, but set up two partitions so I could
>work on either one if I wanted to.  I haven't tried mix-n-match though.

There was a problem a while back, when -STABLE's fsck was unhappy with
the way -CURRENT's fsck left things.  That was quite a while back,
though, and was fixed fairly quickly.

David H. Wolfskill				david at
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