sysrc -- a sysctl(8)-like utility for managing /etc/rc.conf et. al.

[Devin Teske]

On Oct 10, 2010, at 5:15 PM, Garrett Cooper wrote:

> On Sun, Oct 10, 2010 at 3:49 PM, Devin Teske <dteske at vicor.com> wrote:
> 
>> Hmmm, sysctl(9) is lock-free, which might imply that both sysctl(8) and
>> sysctl(3) are also lock-free, and proposed sysrc(8) is lock-free, so might
>> that imply that the atomicity tests would fare the same for all of the
>> above?
> 
> .../sys/kern/kern_sysctl.c says otherwise (look for the comment above
> the sysctllock declaration). The locking is just hidden from the
> developer/end-user.
> 
>> Here's what I'm thinking we should do to solve this...
>> Since the atomicity of the write operation is anything-but singular
>> (meaning, it takes incrementally larger blocks of time to write larger
>> amounts of data, increasing the risk-curve for failure to occur by two
>> operations coinciding at the same time -- I'm truly sorry, my wife has me
>> helping her with her business statistics II course, forgive me, I'll
>> clarify).
> 
> ...
> 
> I think I said it before, but yes.. I completely agree with the
> atomicity approach. I prefer `mktemp /tmp/XXXXXX' because it would do
> nothing more than potentially clutter up /tmp if the operation fails
> for whatever reason (instead of /etc), and it's less of a security
> concern. I suppose that's less of a problem though, because if someone
> has the ability to write to /etc, then all bets are off, but the
> clutter part is a bit annoying..

I checked out mktemp(1)... just what the doctor ordered for preventing race-conditions. And it's in the base FreeBSD distribution even back as far as FreeBSD-4.11 (likely much further; but that's what I checked).



> ...
> 
> I would just hold to this statement in /etc/defaults/rc.conf:
> 
> # All arguments must be in double or single quotes.
> 
> and also state:
> 
> "this tool functions based on the idea that the rc.conf files are
> simply written, and can be evaluated as standalone configuration data.
> Anything that doesn't conform to these requirements isn't guaranteed
> to work with the tool in all cases"

Simpler is indeed better ^_^


> 
> Thanks!
> -Garrett
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--
Cheers,
Devin Teske

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