[NCLUG] Tuesday September 10th, 2019 NCLUG Meeting

[Sean Reifschneider]

Re: Battery Packs:

I saw this video a few weeks ago and it looks like a pretty sweet build for
a battery pack:

https://youtu.be/0jRsltIW8qM

Details: Around $60 for cost, AC plug at 150W, adjustable DC output, 4x
USB, one USB-c, wireless charger.

Thanks for the write-up.

On Tue, Sep 10, 2019 at 11:18 PM Bob Proulx <bob at proulx.com> wrote:

> jdewitt at verinet.com wrote:
> > What: Tuesday September 10th, 2019 NCLUG Meeting
> > When: Tuesday September 10th, 2019, 6pm
> > Where: Fort Collins Creator Hub,
> >   1304 Duff Dr Unit 15, Fort Collins, CO; map:
>
> I arrived on my bicycle slightly late and missed whatever happened at
> the very beginning of the meeting.  Sorry.
>
> Stephen started off the meeting talking about process tracing under
> Linux.  He had a crash problem that he needed to debug.  Initially of
> course he started using strace.  But the overhead of strace is
> significant and it can slow things down.  But then through the course
> of researching the task he discovered auditd.  A much more efficient
> tracing process because it works within the Linux kernel.
>
>   https://people.redhat.com/sgrubb/audit/
>
> Stephen then presented his experiences using it to trace through his X
> server.  Something was killing it.  I imagine that would be quite
> unpleasant!  The auditd tracing looks very interesting because this is
> a tracing feature of the kernel.  Therefore one installs tracing rules
> (somewhat iptables like) and then runs what one wants to trace, the
> kernel traces it to the file, then look at the results that were
> logged.  There are tools to filter the results to narrow down the
> deluge of data into just what one wants to see.
>
> This runs in the kernel with much lower overhead than when using
> strace.  Which is a huge advantage in performance because strace can
> really slow down debugging a process.  Also some processes might
> detect that they are being run under strace and behave differently
> whereas auditd is in the kernel and the process runs exactly the same
> as it would otherwise.  Though perhaps somewhat slower as if they were
> running on a slower system due to the overhead.
>
> Cool stuff!  Check it out!
>
> I then shared some cronjob tricks and traps specially with 'find'.
> Recently a contributed crontab was added that had some inefficiencies
> and noise.  I needed to improve it and talked briefly about some of
> the issues one should be concerned about with tasks run from cron.
> Some hints about how to use 'find' in efficient ways.  Simple but
> hopefully fun and useful tidbits.
>
> Bryan then passed around an early prototype that is he building of his
> DIY video doorbell.  A Raspberry Pi with a camara and a low power
> radar system for motion detection.  Has a speaker and a microphone so
> that he can interact remotely with someone at the door.
>
> Very cool project!  And actually his prototype is nicer looking than
> some of my finished projects.  I need to up my game! :-)
>
> A rousing round of discussion followed.  Among other things we talked
> about the web and web browsers.  Because the web is so pervasive that
> we always degrade to something about a web browser at some point.
>
> James has been working with inexpensive batteries that are available
> now.  Among others are 3.7V Li-ion high density batteries.  People are
> buying these in some bulk and then using them to build high density
> battery packs.  Some show-n-tell.
>
> We decided to go to Red Truck for dinner.
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