Debian 11 on Gigabyte B660M D3H DDR4 board

 I recently setup a Debian 11.2 system on a Gigabyte B660M D3H DDR4. During installation I noticed the onboard networking didn't function.

james@debian11:~$ lspci |grep Ethernet
04:00.0 Ethernet controller: Intel Corporation Ethernet Controller I225-V (rev 03)

With the default 5.10 kernel the module 'igc' for this controller fails with the following error:

root@debian11:/var/log# grep igc messages 

Feb 25 09:44:13 debian11 kernel: [    4.353002] igc: probe of 0000:03:00.0 failed with error -2

The solution for me was to install kernel 5.15 from backports:

root@debian11:/var/log# uname -a

Linux debian11 5.15.0-0.bpo.3-amd64 #1 SMP Debian 5.15.15-2~bpo11+1 (2022-02-03) x86_64 GNU/Linux

root@debian11:/var/log# dmesg |grep igc

[    3.825490] igc 0000:04:00.0: PTM enabled, 4ns granularity

[    3.871312] igc 0000:04:00.0 (unnamed net_device) (uninitialized): PHC added

[    3.930345] igc 0000:04:00.0: 4.000 Gb/s available PCIe bandwidth (5.0 GT/s PCIe x1 link)

[    3.930348] igc 0000:04:00.0 eth0: MAC: d8:5e:d3:91:15:95

[    3.931844] igc 0000:04:00.0 enp4s0: renamed from eth0

[   10.465411] igc 0000:04:00.0 enp4s0: NIC Link is Up 1000 Mbps Full Duplex, Flow Control: RX/TX

You'll temporarily need an alternative network controller to install and update the system. I used a USB adapter that I have on hand for such problems. 

Plotting an image in MATLAB and maintaining the original size

This worked for me:

 https://stackoverflow.com/questions/1848176/how-do-i-save-a-plotted-image-and-maintain-the-original-image-size-in-matlab

I = imread('peppers.png');      %# Load a sample image
imshow(I);                      %# Display it
[r,c,d] = size(I);              %# Get the image size
set(gca,'Units','normalized','Position',[0 0 1 1]);  %# Modify axes size
set(gcf,'Units','pixels','Position',[200 200 c r]);  %# Modify figure size
hold on;
plot(100,100,'r*');             %# Plot something over the image
f = getframe(gcf);              %# Capture the current window
imwrite(f.cdata,'image2.jpg');  %# Save the frame data

Internals of Ubiquiti ETH-SP ethernet surge protector

 A couple of photos showing the internals of Ubiquiti's Ethernet surge protector ETH-SP. 

There are eight 2RL090 90 Volt GDTs.  One between each Ethernet line and the metal grounding point.  

HTTP Time protocol

The HTTP Time Protocol (HTP) is used to synchronize a computer's time with web servers as reference time source. Very handy in situations where NTP UDP/123 is being blocked. http://www.vervest.org/htp/

Electrical Cable sizing calculator for AS/NZS3008

https://www.jcalc.net/cable-sizing-calculator-as3008

A nice write up on using and crimping wire ferrules.

Nagios plugin for monitoring last modified time stamps of website content

Inspired by this plugin and this discussion,  I have written a nagios plugin for monitoring the "Last-Modified" time of content on a website. The script uses curl to retrieve the header information and then warns if the content has not been updated within a specified period of time.   

I developed this plugin for checking that data & satellite plots on our aurora alert site were being refreshed at the expected intervals.

[james@orchid tmp]$ curl -s -I  http://auroraalert.otago.ac.nz/aurora/Suomi_NPP_DNBNCC_night_highresimage.png
HTTP/1.1 200 OK
Date: Tue, 14 Aug 2018 23:36:08 GMT
Server: Apache/2.4.6 (CentOS)
Last-Modified: Tue, 14 Aug 2018 05:56:06 GMT
ETag: "15cfb4-5735edda8345f"
Accept-Ranges: bytes
Content-Length: 1429428
Content-Type: image/png

 Nagios plugin shell script:

#!/usr/bin/env bash

DEFAULT_WARN_SECONDS=600
DEFAULT_CRIT_SECONDS=1200

while getopts  'hp:c:w:' option; do
    case $option in
        h) help=1;;
        p) path=$OPTARG;;
        c) crit=$OPTARG;;
        w) warn=$OPTARG;;
    esac
done
if [ -n "$help" ] || [ -z "$path" ]; then
    echo "usage: $0 -p [path (required)] -w [warning threshhold seconds] -c [critical threshold seconds]" 1>&2
    exit 3

fi
if [ -z "$warn" ]; then
    warn=$DEFAULT_WARN_SECONDS
fi
if [ -z "$crit" ]; then
    crit=$DEFAULT_CRIT_SECONDS
fi
modificationTimeStamp() {
    curl -s -I HEAD $path |
        awk '/Last-Modified/{ date=""; for(i=2;i<=NF;++i) date=(date " " $i); print date;}' |
        xargs -I{} date -d {} +"%s"
}
#seconds=$(($(date +'%s') - $(stat --format='%Y' $path)))
seconds=$(($(date +'%s') - $(modificationTimeStamp) ))
if [ $seconds -gt $crit ]; then
    echo "CRITICAL: $path was last modified $seconds seconds ago"
    exit 2
elif [ $seconds -gt $warn ]; then
    echo "WARNING: $path was last modified $seconds seconds ago"
    exit 1
else
    echo "OK: $path was last modified $seconds seconds ago"
    exit 0
fi

Add it to the command.cfg

#check last modified time on remote URL
define command{
        command_name    check_urlmtime
        command_line    $USER1$/check_urlmtime -p $ARG1$ -w $ARG2$ -c $ARG3$
        }

Example service entry

define service{
        use             generic-service         ; Inherit default values from a template
        host_name               auroraalert
        service_description     Soumi NPP satellite image
        check_command   check_urlmtime!"http://auroraalert.otago.ac.nz/aurora/Suomi_NPP_DNBNCC_night_highresimage.png"!86400!172800
        }