Entries by Raymond P. Burkholder

Matt Oswalt has an article called ESXi vSwitch Load Balancing Woes where he deep dives into VMware's ESXi virtual switch and, based upon personal experience, discusses port channels, hash algorithm selection, and path selection. I need to refer back to this to see if networks I've seen conform to what he discusses.

From How do I find the build dependencies of a package?, there are some commands for finding build package dependencies:

• full list of dependencies: apt-rdepends --build-depends openoffice.org
• dependencies not installed: apt-rdepends --build-depends --print-state openoffice.org | grep NotInstalled
• dependencies for top most package: apt-rdepends --build-depends --follow=DEPENDS
• show control file for source: apt-cache showsrc | grep ^Build-Depends

A document of suggestions to help make email more secure:

Email security and anti-spoofing

Talks about TLS, DKIM, DMARC and SPF with a few barebone configuration examples.

How many subscribe to scholarly things like 'Communications of the ACM'? or the 'IEEE Spectrum'?

I then I took it one step further and sat at a table by myself down at the club, and read it cover to cover. With a beer or two.

And something that hasn't happened in a long time, or well, ever, I got called out as a sterotype: looking like a geek from San Francisco. Well, that was what the woman, who also had no conversational partner, used to strike up a conversation.

Anyway, back to the magazine, who would have thought, that in the CACM, you see such interesting things like:

"Divination is the practice of occultic ritual as an aid in decision making", on page 7 no less. Which goes on to say that "... divination truly allows us to consult the divine, we can view it simply as a form of randomization, which is recognized as a powerful construct in game theory, and algorithm design." ... "randomization is a powerful way to deal with incomplete information" ... "they are simply randomizing in the face of uncertainty about rain, pests, and more, but this randomization comes with a belief in the divine source of the decision".... "when the accept/reject decision pivots on issues such as significance and interestingness, which can be quite subjective".

Another article: "Assuring Software Quality by Preventing Neglect".... which is a 'grayhat' problem when compared to blackhats (hackers who deploy software as a weapon with malicious intent) and whitehats (setting safeguards against defective products)". With a few interesting conversation starters being, I think: ".... during maintenance cycles, they do not correct the old source code comments, seeing such edits as risky and presumptuous". ... "it is a failure of degree, a failure to pay enough attention and take enough trouble" ... which leads to a theory of "ethics of care which displaces the classical agent centered morality of duty and justice, enduring patient-centered morality as manifest real-time in relationships".

And, well, something which probably everyone knows, but has been evolving through a series of articles in the magazine, is that machine learning algorithms require training time via "generative adversarial networks", which means you need to introduce some sneaky garbage to improve the odds of appropriate machine learning and matching black boxes.

And another, in which I can personally associate: "Multitasking Without Thrashing". "Human context switching is more complicated than computer context switching. Whereas the computer context switch replaces a fixed number of bytes in a few CPU registers, the human has to recall what was 'on the mind' at the time of the switch, and, if the human was interrupted with no opportunity to choose a 'clean break', the human has to reconstruct lost short term memory" ... "if you have several important tasks, your brain can get stuck in a decision process that can take quite a long time to decide -- a situation known as the choice uncertainty problem". ... "thrashing happens to human multi-taskers when they have too many incomplete tasks. They fall into mood of 'overwhelm' in which they experience considerable stress" ..... "context switching is _not_ the cause of thrashing. ... the cause of thrashing is the failure to give every active task enough space for its working set" ... "when a task's working set is in your workspace, protect it from being unloaded as long as the task is active .. analog: protect working sets of active tasks and do not steal from other tasks". ... which leads to the rather obvious conclusion: "to exit the thrashing state, you need to reduce demand or increase your capacity".

Ok one more: "what we have instead is a society moving towards prosthetic brains that can be monitored at all times by the state, without the inconvenience of having to have everyone check in each day at the police station". When you read this, were you thinking "this isn't me! This isn't now!"? Well, even in present time, this is visible by what we write, where we write, what we read, where we read, who we interact with, what we interact with, ....

• Mark Wagner: performance tuning
• DPDK: How to get best performance with NICs on Intel platforms
• CloudFlare: How to achieve low latency with 10Gbps Ethernet

But then again, all this is probably old hat, and may have changed for 40gbps adapters. What about the Mellanox Connect-X 5 100 gbps adapters?

Debian Installer is a complicated tool. I am trying to figure out where to start. Well, some starting pages:

• DebianInstaller: starting page for many things debian installer
• DebianInstaller Preseed: various ways to get preseed files to the debian installer
• Debian Testing Install
• Netboot: the daily release version
• Debian Installer Internals: read to understand what happens during the installation process

To troubleshoot some recent Buster installation problems, I know now to use DEBCONF_DEBUG=5 in my boot files.

Debian Git Server, which includes debian installer packages.

A Check_MK plugin which is supplied as part of the standard install but not 'turned on' is the 'smart' agent. It is a plugin which resides on the target with hard-drives to be monitored. Temperatures and other useful statistics can be collected.

The plugin can be found in the share/check_mk/agents/plugins/ directory amongst a number of other useful plugins.

It needs to be copied to the /usr/lib/check_mk_agent/plugins/ directory on the target to be monitored.

In order to be useful, the 'smartmontools' package needs to be installed as a pre-requisite.

On one of my systems, I get output some output similar to:

SMART WDC_WD1003FZEX-00K3CA0_WD-WCC6Y3PN9XKC Stats
  OK - Powered on: 3529 hours, Power cycles: 51, Reallocated sectors: 0, 
  Reallocated events: 0 (was 0 during discovery: normalized value looks OK), 
  Spin retries: 0, Pending sectors: 0, UDMA CRC errors: 0
Temperature SMART WDC_WD1003FZEX-00K3CA0_WD-WCC6Y3PN9XKC
  OK - 30 °C

Values are charted as well.

To get at various hardware sensors like temperatures and voltages, it is typically necessary to install the 'lm-sensors' package. Once the package is installed, sensors can be auto-detected with:

sensors-detect --auto

A variation of that is:

yes | sensors-detect

At the end of the output, this will probably generate an output similar to:

To load everything that is needed, add this to /etc/modules:
#----cut here----
# Chip drivers
coretemp
#----cut here----

'modprobe coretemp' can be used to obtain instant gratification by loading the module interactively, instead of at the next reboot.

On a simple system, some values can be seen:

# sensors
acpitz-virtual-0
Adapter: Virtual device
temp1:        +27.8°C  (crit = +105.0°C)
temp2:        +29.8°C  (crit = +105.0°C)

coretemp-isa-0000
Adapter: ISA adapter
Package id 0:  +50.0°C  (high = +105.0°C, crit = +105.0°C)
Core 0:        +49.0°C  (high = +105.0°C, crit = +105.0°C)
Core 1:        +48.0°C  (high = +105.0°C, crit = +105.0°C)

For obtaining an output suitable for scraping by a check_mk agent, a different format can be emitted:

# sensors -u
acpitz-virtual-0
Adapter: Virtual device
temp1:
  temp1_input: 27.800
  temp1_crit: 105.000
temp2:
  temp2_input: 29.800
  temp2_crit: 105.000

coretemp-isa-0000
Adapter: ISA adapter
Package id 0:
  temp1_input: 49.000
  temp1_max: 105.000
  temp1_crit: 105.000
  temp1_crit_alarm: 0.000
Core 0:
  temp2_input: 48.000
  temp2_max: 105.000
  temp2_crit: 105.000
  temp2_crit_alarm: 0.000
Core 1:
  temp3_input: 48.000
  temp3_max: 105.000
  temp3_crit: 105.000
  temp3_crit_alarm: 0.000

While writing this article, a few interesting web sites were encountered:

• Arch Linux' Sensors Page
• Plugins for Check_MK
• Check_MK plugin: lmsensors: a place to which I need to return and try installing his plugin for more information display in Check_MK.
• Earlier Article I wrote doing something similar but different.

I use an app called 'psensor' for watching system temperatures in a chart form.

OMD is a collection of monitoring tools which include the Check_MK monitoring application. Check_MK is a series of Python scripts and agents designed to simplify the use of a Nagios based scanning engine.

I have a small server running Debian Buster. I have used LXC to build a container. I used the following command to build a container:

lxc-create -n omd  -f /var/lib/lxc/persist/omd/config -t debian -B btrfs -- -r stretch

I have a BTRFS filesystem mounted on /var/lib/lxc. the -B btrfs creates a BTRFS subvolume for the container, which allows snapshots and the like.

The config file looks something like:

# cat /var/lib/lxc/persist/omd/config 
# 20171015
# lxc-create -n omd  -f /var/lib/lxc/persist/omd/config -t debian -B btrfs -- -r stretch
lxc.utsname = omd
lxc.start.auto = 1
lxc.start.order = 5
lxc.start.delay = 1

lxc.network.type = veth
lxc.network.name = eth50
lxc.network.veth.pair = veth-omd-v50
lxc.network.hwaddr = 0a:00:40:50:00:xx
lxc.network.ipv4 = 10.0.10.201/24
lxc.network.ipv4.gateway = 10.0.10.254
lxc.network.script.up = /etc/lxc/ovsup.sh
lxc.network.script.down = /etc/lxc/ovsdn.sh
lxc.network.flags = up

I am using Open vSwitch to provide bridging capabilities to the container and its environs. This particular container, using the lxc.start.auto value, will auto-start when the host restarts.

Yesterday, I attempted to install the Buster version of OMD, but some package dependencies were stale (repository) , and since I didn't have time to troubleshoot that, I went with the stable Stretch version:

apt install nano bash-completion gnupg2 wget
wget --no-check-certificate https://labs.consol.de/repo/stable/RPM-GPG-KEY
apt-key add RPM-GPG-KEY
echo "deb http://labs.consol.de/repo/stable/debian stretch main" > /etc/apt/sources.list.d/labs-consol-stable.list
apt update
apt install omd

It is as easy as that.

To configure a monitoring instance:

omd setup
omd create site01
omd config site01
omd start site01
su - site01
nano etc/check_mk/main.mk

During the 'omd create site01' step, I select the Nagios 3 engine, and set the Check_MK interface as default.

The next experiment is to install the Raw Version and see how that differs.

Two articles from Planet Debian on the same subject, which has been plaguing me as well. There might just be a solution.

• No more no surprises
• Fixing vim in Debian

Debian has generally always had, as a rule, “sane defaults” and “no surprises”. This was completely shattered for me when Vim decided to hijack the mouse from my terminal and break all copy/paste functionality. This has occured since the release of Debian 9.

The solution might be installing in .vimrc:

if !has("gui_running")
  set mouse=
endif

Petter Reinholdtsen mentions Generating 3D prints in Debian using Cura and Slic3r(-prusa).

He has a link to Cura which "3D printer / slicing GUI built on top of the Uranium framework"

Just linking to other sites which have links to other sites:

• 50+ Sites for Finding Remote Jobs as of September 20,2017
• Top Alternative Sites like Microworkers
• 25 Top Job Sites for Freelance Gigs as of November 22, 2015

Don’t bore me: how to write a technical work history that matters

Monitoring buffer queues has had a recent update on Cumulus running on Mellanox swtiches using watermark values to determine what happens during microbursts.

Also on the same site is a page devoted to documenting Buffer Queue Sizes in various switch lines.

The Energy Sciences Network has a number articles (plus many other things):

• Linux Tuning which includes TCP tuning entries, as well as congestion control entries.
• Even an entry on 40G/100G Tuning

I am more into nftables now-a-days (which just had release 0.8 in the last couple days), but maybe these iptables/xtaqbles thingies can be made to work in nftables:

• Xtables-Addons On Centos 6 & Iptables GeoIP Filtering
• search for 'tarpit nftables' and see if there is anything, it is an interesting sticky concept
• A series of Xtables-addons. It would be interesting which of them could be re-implemented with nftables functionality.