Entries by Raymond P. Burkholder

The key is the 'ether' specifier. The -e option shows the mac address in the output:

$ sudo tcpdump -n -i vlan50 ether host e4:54:e8:29:44:2d or ether host ff:ff:ff:ff:ff:ff -vv -e

I had this error when trying to EUFI boot with IPXE against a DNSMasq server:

Filename: bootnetx64.efi
tftp://10.x.x.x/bootnetx64.efi... ok
bootnetx64.efi : 1322936 byes [EFI]
Fetching Netboot Image
Malformed binary after Attribute Certificate Table
datasize: 4194034 SumOfBytesHashed: 1253376 SecDir->Sisze: 1392
hashsize: 2939536 SecDir->VirtualAddress: 0x00132000
Failed to load image: Invalid Parameter
start_image() returned Invalid Paramter
Could not boot image: Error 0x7f048282 (http://ipxe.org/7f048282)

The issue is that I had grubx64.efi and bootnetx64.efi incorrectly positioned in /etc/dnsmasq.d/local. This is the correct statement placement:

dhcp-match=set:efi-bc,option:client-arch,7
dhcp-boot=tag:efi-bc,grubx64.efi
pxe-service=tag:efi-bc,BC_EFI, "Install,bc", bootnetx64.efi,

WARNING: performing these operations can be dangerous to desired data. Be careful against which drives you apply these commands.

Acquire current geometry:

$ sudo sfdisk -d /dev/sda
label: dos
label-id: 0x1bc93b71
device: /dev/sda
unit: sectors
sector-size: 512

/dev/sda1 : start=        2048, size=      524288, type=b

$ sudo sfdisk -d /dev/sda > sda.txt

Kill the partition table (dangerous!):

$ sudo dd if=/dev/zero of=/dev/sda count=1 bs=512
1+0 records in
1+0 records out
512 bytes copied, 0.00642451 s, 79.7 kB/s

$ sudo fdisk -l /dev/sda
Disk /dev/sda: 57.73 GiB, 61984505856 bytes, 121063488 sectors
Disk model: DataTraveler 2.0
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes

Rebuild the drive, equally dangerous, but with some backup with the -O:

$ sudo sfdisk -O sfdisk.save /dev/sda < sda.txt
Checking that no-one is using this disk right now ... OK

Disk /dev/sda: 57.73 GiB, 61984505856 bytes, 121063488 sectors
Disk model: DataTraveler 2.0
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes

>>> Script header accepted.
>>> Script header accepted.
>>> Script header accepted.
>>> Script header accepted.
>>> Script header accepted.
>>> Created a new DOS disklabel with disk identifier 0x1bc93b71.
/dev/sda1: Created a new partition 1 of type 'W95 FAT32' and of size 256 MiB.
Partition #1 contains a vfat signature.
/dev/sda2: Done.

New situation:
Disklabel type: dos
Disk identifier: 0x1bc93b71

Device     Boot Start    End Sectors  Size Id Type
/dev/sda1        2048 526335  524288  256M  b W95 FAT32

The partition table has been altered.
Calling ioctl() to re-read partition table.
Syncing disks.

Check the partition tables;

$ sudo fdisk -l /dev/sda
Disk /dev/sda: 57.73 GiB, 61984505856 bytes, 121063488 sectors
Disk model: DataTraveler 2.0
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disklabel type: dos
Disk identifier: 0x1bc93b71

Device     Boot Start    End Sectors  Size Id Type
/dev/sda1        2048 526335  524288  256M  b W95 FAT32

Format the filesystem:

$ sudo mkfs -t vfat /dev/sda1
mkfs.fat 4.1 (2017-01-24)

user manual for sfdisk, which learned about at How to run fdisk in non-interactive batch mode.

I used fdisk /dev/sda to create the initial flavour of the vfat 256MB drive. Not much space is required to build a disk for ipxe boot operations (using a Dell Wyse 3040 ThinClient which does not seem to know how to PXE boot natively).

$ mkdir mnt
$ sudo mount -o loop ~/Downloads/iso/debian-10.7.0-amd64-netinst.iso mnt
$ ls mnt
$ sudo umount mnt

The command wipefs can be used to examine the read partition boot-signatures, and possible 'kill' them.

# wipefs /dev/sda
DEVICE OFFSET      TYPE    UUID                   LABEL
sda    0x36        vfat    D14A-DCD7
sda    0x0         vfat    D14A-DCD7
sda    0x1fe       vfat    D14A-DCD7
sda    0x8001      iso9660 2020-02-25-20-44-34-00 ISOIMAGE
sda    0xe6e907e00 gpt

# dd if=/dev/zero of=/dev/sda bs=512 count=1
1+0 records in
1+0 records out
512 bytes copied, 0.00808424 s, 63.3 kB/s

# wipefs /dev/sda
DEVICE OFFSET      TYPE    UUID                   LABEL
sda    0x8001      iso9660 2020-02-25-20-44-34-00 ISOIMAGE
sda    0xe6e907e00 gpt

# wipefs -a /dev/sda
/dev/sda: 5 bytes were erased at offset 0x00008001 (iso9660): 43 44 30 30 31
/dev/sda: 8 bytes were erased at offset 0xe6e907e00 (gpt): 45 46 49 20 50 41 52 54
/dev/sda: calling ioctl to re-read partition table: Success

# wipefs /dev/sda

WipeFS Documentation

Since none of this is registered in github, here is my alternate mechanism for 'staring' these items:

• FreeCAD - open-source parametric 3D modeler made primarily to design real-life objects of any size. Parametric modeling allows you to easily modify your design by going back into your model history and changing its parameters. You get modern Finite Element Analysis (FEA) tools, experimental CFD, dedicated BIM, Geodata or CAM/CNC workbenches, a robot simulation module that allows you to study robot movements and many more features.
• cppyy: Automatic Python-C++ bindings - an automatic, run-time, Python-C++ bindings generator, for calling C++ from Python and Python from C++
• Open CASCADE Technology, The Open Source 3D Modeling Libraries - is a software development kit (SDK) intended for development of applications dealing with 3D CAD data or requiring industrial 3D capabilities. It includes a set of C++ class libraries providing services for 3D surface and solid modeling, CAD data exchange, and visualization. tutorial
• OpenStudio is a cross-platform (Windows, Mac, and Linux) collection of software tools to support whole building energy modeling using EnergyPlus and advanced daylight analysis using Radiance.
• Topologic is a software development kit and plug-in that enables logical, hierarchical and topological representation of spaces and entities

From an article on phoronix about Linux Developers Ponder Decade-Old Decision To Disable PCI Runtime Power Management By Default, the comments section has some useful remarks about power management and tuning.

The kernel has some documentation: sysfs devices power.

An initial scan: Continue reading "Power Adjustability" »

In military thinking, there is a simple framework of four types of knowing:

• There are things you know that you know.
• There are things you know that you don't know but you can know them, by reading, listening, talking to somebody, and so on.
• There are unknown knowns. There are things which you definitely are going to know someday, for example, the cause of somebody's death before it happens. However, you don't know it now.
• There are unknown unknowns. There are threats, which you don't know, which in turn you don't know they exist. Once they come, you don't know which form they take.

Unfortunately, with security, it gets worse. With these four vectors, we've got another four types of knowing:

• We can stay confused.
• We can stay in doubt for what we do.
• We can stay afraid of compliance punishments, security risks. Your boss being angry at you overspending your budget.
• We can be risk averse. We can just pretend that nothing is wrong.

Reference: Designing Secure Architectures the Modern Way, Regardless of Stack

Notable link: Implementing a Staged Approach to Evolutionary Architecture

With some help from Learn Git Branching, here is are some 'Coles Notes':

Create a new branch:

git branch _branch_name_

Check out the new branch (for subsequent commits)

git checkout _branch_name_

Switch to the new branch (for subsequent commits, an alternative to checkout)

git switch _branch_name_

Create a new branch and check it out at the same time:

git checkout -b _branch_name_

Merging in Git creates a special commit that has two unique parents. A commit with two parents essentially means "I want to include all the work from this parent over here and this one over here, and the set of all their parents." To merge a branch into main/master, first checkout / switch to the primary branch.

git merge _branch_name_

Rebasing essentially takes a set of commits, "copies" them, and plops them down somewhere else. While this sounds confusing, the advantage of rebasing is that it can be used to make a nice linear sequence of commits. The commit log / history of the repository will be a lot cleaner if only rebasing is allowed.

git switch _branch_name_;git rebase master

To move back in time relative to a branch:

git checkout _branch_name_^

To move back in time relative to HEAD:

git checkout HEAD^

To move back in time relative a number of steps:

git checkout _branch_name_~2

Use relative refs to move a branch around:

git branch -f master HEAD~3

A git reset will move a branch backwards as if the commit had never been made in the first place. It is useful for local branches.

git reset HEAD~1

Git reset doesn't work for remote branches that others are using. In order to reverse changes and share those reversed changes with others, we need to use git revert.

git revert HEAD

To cherry-pick, means copy a series of commits below your current location (HEAD):

git cherry-pick _branch_name_1_ _branch_name_n_

Interactive rebase provides rebasing interactively to re-arrange and delete commits:

git rebase -i HEAD~4

HEAD can be modified with:

git commit --amend

Since my NFDump/DFSen Upgrade post many moons ago, I am once again doing an install for analyzing Netflow, this time on a server running Open vSwitch (OVS).

NFDump is a netflow collector. NFSen analyzes the netflow entries captured by NFDump.

Installing NFDump is easy using Debian's package:

apt install nfdump
systemctl stop nfdump
systemctl disable nfdump

The last two lines stop and disable the default service. Service control is provided with NFSen.

From a visualization perspective, there are a number of possibilities:

• NFSen Documentation is the main starting page for the code at SourceForge.
• NFSen on Github is p-alik's unofficial updated version of the original repository - my preferred location as it has some primary bug fixes and stays with the times
• mbolli / nfsen-ng - a modernized version of NFSen but doesn't appear to have the flexible query capability
• robcowart / elastiflow - I saw a link to this from Netflow collection and visualization with Elastiflow - which may have not relationship to NFDump / NFSen but seems promising none-the-less. Installation notes are at Installing Elastiflow flow monitoring solution.

From an NFSen perspective, here are the steps I used on a Debian Bullseye installation:

apt install wget less vim
apt install php rrdtool  librrd-dev librrds-perl php-rrd
apt install libmailtools-perl
apt install libsocket6-perl
apt install git
cd /usr/src
git clone https://github.com/p-alik/nfsen.git
cd nfsen
cp etc/nfsen-dist.conf etc/nfsen.conf
vim etc/nfsen.conf
./install.pl ./etc/nfsen.conf
/usr/local/bin/nfsen start
diff nfsen-dist.conf nfsen.conf

These are the changes to the nfsen.conf file: Continue reading "Netflow with NFDUMP, NFSEN and Open vSwitch and..." »

Is it possible to shift+page-up to reveal the backtrace? The backtrace section ends with "---[ end trace 75435… ]---" If that's not possible, see if you can get a copy from /var/log after rebooting with a working kernel or when using a network disk. If that's not possible, and you have good reflexes, you could try ctr+s or scroll-lock to pause the kernel output at just the right moment, but it's probably easier to just set up remote logs:

https://wiki.debian.org/Rsyslog

• MySensors Hardware
• OpenHardware.io
• ESP8266 Wiki - sleeping the ESP8266
• Arduino - 3.5A DC DC Buck converter, USR-ES1 W5500 SPI / Ethernet
• ESP32-POE
• freetroinics Power over Ethernet for Arduino

From my experience it's actively monitored by an individual named Devlin Null. His friends call him Dev.

Dev's backup is Helen Waite. If you expect them to take action, you can go to Helen Waite.

I'm looking for a do-all home system, something to store camera video, maybe act as media center, and host some files. This maybe over-kill, but this is what I came up with so far

I did some searching through Reddit's Small Form Factor PC, I picked up a few ideas. Most pointed idea was the link for PCPartPicker to look for Mini-ITX boards with ECC memory. I first looked at the Asus P11C-I, but it didn't have any HDMI or Display Ports, which force the use of a Graphics card. But I did like their CPU Listing site for selecting CPUs.

There was the ASRock Rack Motherboard C236 WSI, but it doesn't appear to have a location for an M.2 storage card.

But the selector didn't show what I was looking for. In a reddit post I came across GigaByte C246N-WU2 which suits my needs better.

• GIGABYTE C246N-WU2 LGA 1151 (300 Series) Intel C246 SATA 6Gb/s Mini ITX Intel Motherboard
• Intel Xeon E-2176G Coffee Lake 3.70 GHz LGA-1151 80W CM8068403380018 Server Processor Intel UHD Graphics P630 - maybe overkill, and 80W, more than the recommended 65W for the case
• Crucial 16GB DDR4 SDRAM ECC Unbuffered DDR4 2666 (PC4 21300) Server Memory CT16G4WFD8266
• Fractal Design Node 202 case. Some discussion on fans - may need a custom 3D duct for short CPU fan. 202 designs. more fan stuff
• Noctua NH-L9i fan (but may need a printed 3D duct)
• Western Digital WD BLACK SN750 NVMe M.2 2280 1TB PCI-Express 3.0 x4 64-layer 3D NAND Internal Solid State Drive (SSD)
• CORSAIR SF Series SF450 450W 80 PLUS GOLD Active PFC SFX SFX12V Micro ATX Full Modular Power Supply
• Total: CDN $2000

As a reference, there is also SFF.Network for small form factor systems.

Chassis
• Premium Builds has some MiniITX case suggestions.
• Supermicro Superchassis CSE-721TQ-250B Mini-Tower with 250W Power Supply - seems to have good airflow
• SilverStone but their airflow doesn't look good