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

[Garrett Cooper]

On Sat, Oct 9, 2010 at 10:36 AM, Devin Teske <dteske at vicor.com> wrote:
>
> On Oct 9, 2010, at 10:03 AM, Garrett Cooper wrote:
>
>> On Thu, Oct 7, 2010 at 12:54 AM, Julian Elischer <julian at freebsd.org> wrote:
>>>  On 10/7/10 12:23 AM, jhell wrote:
>>>>
>>>> Alright thank you for your explanation. I do not normally see this usage
>>>> and this just sort of stood out at me and I did not want to assume what
>>>> you were trying to accomplish, without asking.
>>>
>>> three useage cases come to mind immediately.
>>>
>>> 1/ use within other scripts..
>>>  instead of the dozens of homegrown solutions people have written for puting
>>> something
>>> into /etc/rc.conf  one can use this.
>>>
>>> 2/ what is the value of X on machines a,b,c
>>>  foreach machine in a b c
>>>  do
>>>      ssh $machine sysrc X
>>>  done
>>>
>>>    you may well say "you could have used grep" bu tgrep doesn't give the
>>> default value vie the
>>>   hierachy of .rc files.
>>> 2A is of course to correc teh values found to be wrong with (2)
>>>
>>> 3/ on a really small system, without an editor this may do a cleaner job
>>> than the usual
>>>  "grep -v X /etc/rc.conf >/tmp/x;echo X >> /tmp/x; mv /tmp/x /etc/rc.conf"
>>
>>    I was going to say...
>>
>> 3A On a system where you're logged in via singleuser, sometimes
>> terminal settings don't work correctly with editors (these days it's
>> mostly because /usr isn't available so it can't load ncurses apps,
>> some libs, termcap, etc). That would be a lifesaver in this case.
>
> I hadn't realized that. That's stupendous!
>
> Though I do believe that `/rescue/vi' exists these days as a statically-linked binary (built using crunchgen(1) via `rescue/rescue/Makefile' in the FreeBSD source tree).

Yeah, but unfortunately if some filesystems aren't mounted [ /usr,
/var, etc ] back in the 5.x days (that's when I got into FreeBSD)
[until recently after ed@'s work on syscons and libteken?], most
utilities like vi and ee are braindead when it comes to printing
characters on the screen. I've screwed up and forgot to put down nfs
shares as noauto a few times, and also tinkered around with ata <->
ahci within the past couple months, so until I learned enough sed to
comment out lines in fstab, booting up my system didn't work out too
well :/.

>>    But then I realized that this command probably would live in
>> /usr/sbin and would probably need other apps in /usr/bin // /usr/sbin
>> to run this command :).
>
> I envisioned it living in `/sbin' and it's actually free of dependencies to external executables. If you execute it with the "-d" option ('d' for 'dependencies'), you can see that it uses only shell internals. The only thing this script truly depends on is `/bin/sh'. So it sounds like it would fit the ability of working within single-user mode quite well (remember, I developed it for embedded systems -- where things like grep/sed/awk may even be missing).

Guess it goes to show that I should review the code :).

Thanks!
-Garrett