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Date: Tue, 1 Jan 2013 15:13:28 -0600 (CST)
From: Robert Bonomi <bonomi@mail.r-bonomi.com>
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To: fbsd8@a1poweruser.com, freebsd-questions@freebsd.org
Subject: Re: Changing value of uname -r
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> From owner-freebsd-questions@freebsd.org  Tue Jan  1 11:52:49 2013
> Date: Tue, 01 Jan 2013 12:49:17 -0500
> From: Fbsd8 <fbsd8@a1poweruser.com>
> To: FreeBSD Questions <freebsd-questions@freebsd.org>
> Subject: Changing value of uname -r
>
> uname -r   returns 10.0-CURRENT
>
> setenv UNAME_r "9.0-RELEASE"
>
> uname -r   now returns 9.0-RELEASE
>
> How to reset uname -r to original value without doing
> setenv UNAME_r "10.0-CURRENT"?
>
> Is there some way just to deactivate the effect of the
> setenv UNAME_r so it returns to the real value of the system?

Did you try:
  unsetenv UNAME_r

If yes, what were the results?

If no, _why_not_?