[NCLUG] Tuesday September 10th, 2019 NCLUG Meeting

[Bob Proulx]

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.