Entries by Raymond P. Burkholder

When one doesn't know the keystroke to get into the BIOS, one handy command to reboot from Linux:

# systemctl reboot --firmware-setup

zram, formerly called compcache, is a Linux kernel module for creating a compressed block device in RAM, i.e. a RAM disk, but with on-the-fly “disk” compression. Debian has a init system file for it.

I'm one of those who use zsmalloc as a module - mainly because I use zram as a compressing general purpose block device, not as a swap device. I create zram0, mkfs, mount, checkout and compile code, once done - umount, rmmod. This reduces the number of writes to SSD. Some people use tmpfs, but zram device(-s) can be much larger in size. That's a niche use case and I'm not against the patch.

Running out of RAM in Ubuntu? Enable ZRAM -

When using some relatively inexpensive parts to build a test three server Ceph solution, it seems that drive controllers and SSD drive combinations are finicky. Specifically, it seems that a Dell H310 controller may have issues with some or all Samsung SSD drives.

At Slow writes PERC H700 and Samsung 850 PRO SSD, a Dell response indicates:

The Samsung 850 Pro SSDs are not validated or certified to work with Dell controllers and as such there is a communication mismatch between the drives and the controller at the firmware level. As a result, you are bound to realize unexpected poor Read and Write performance regardless of controller cache settings.

It said that the Samsung 840 drive will work with the controllers. With Broadcom taking over LSI, they've removed old links, so documents are hard to find now. In trying to follow a document trail:

• Dell PowerEdge RAID Controller (PERC) H310, H710, H710P, and H810User’s Guide on page 9 says the H310 has an LSI2008 chipset. I'm looking at the H310 as it provides for direct passthrough to the drives with out RAID. The card has no caching.
• LSI SAS 2008 RAID Controller/ HBA Information - An H310 is similar to the LSI9211-8i
• Check Interoperability and Compatibility

To use the H310 for non-cache passthrough, it is recommended to flash the card in IT mode. I'll try this once I obtain the card. In the meantime, some possibly relevant links to the drivers and process:

• Disk Controller features and Queue Depth? - from 2014, discusses queue depth and diagnostic commands.
• Flashing the H310 Mono Mini to IT mode has a link to probably the best link to a flashing tutorial. But is complicated for flashing the mini H310. From the notes: the R610 is an 11th generation server, and when the mini H310 is reflashed to IT mode, the server probably won't reboot.
• Crossflashing the Dell PERC H200 and H310 to the LSI 9211-8i (from year 2018) implies that the H310 is the equivalent of an LSI 9211-8i. Also, a Dell H200 and an H310 must be similar from a firmware perspective.
• Flashing IT Firmware to the LSI SAS9211-8i HBA - 2012 - flash to a pci card
• How to crossflash PERC H310 to IT mode LSI 9211-8i firmware (HBA for FreeNAS, UnRAID) - an article from 2017 with better, more native instructions
• Crossflash Dell PERC H310 to LSI 9211-8i IT Mode Using Legacy (DOS) and UEFI Method (HBA Firmware + BIOS)
• PERC H310 - LSI 9211-8i - $50 - notes on purchase, install, and upgrade of card.
• Problems Flashing Dell Perc H310 - discusses H310 in PCI slot instead
• How-to Flash Dell Perc H310 with IT Firmware To Change Queue Depth from 25 to 600
• Updated: SAS HBA crossflashing or flashing to IT mode, Dell Perc H200 and H310 from 2016 where is is suggested that "Integrated, Mini or Mini Mono Perc H310 do NOT try to crossflash with these steps".
• DELL PERC H310/H710/H710P/H810 Controllers driver version 5.1.112.64,A00 - a starting point for the search of appropriate drivers
• LINUX PERCCLI Utility For All Dell HBA/PERC Controllers - and the starting point for command line utilities
• LSI MegaRAID SAS - some notes on the CLI utilities
• Doing battle with a Dell R620 and Ubuntu - has some remarks on H310 testing.
• H310 and Fan Noise
• Low random read/write on samsung 840 250gb ssd - spectre bios upgrades can destroy random read/write times

Drive Information:

• Don't do it: consumer-grade solid-state drives (SSD) in Storage Spaces Direct
• Ceph: how to test if your SSD is suitable as a journal device?
• High-performance cluster storage for IOPS-intensive workloads

Cluster test:

rados bench -p vm_storage 10 write -b 4M -t 16"

It is said that fruits and vegetables need to be washed prior to use. Yes, washing can probably get rid of most dirt and grind, but does washing actually make vegetables and fruit safer? Is there a better way to remove pathogenic microorganisms?

I came across How to eat raw beet greens safely? where there is a section discussing "Vinegar, salt, warm water to fight pathogens":

Vinegar has an antibacterial action, inhibiting bacterial growth.

In a study, scientists combined the use of vinegar and sodium chloride (salt). This solution was effective for the prevention of bacterial food poisoning.

Another study measured the effectiveness of vinegar against bacteria, such as Escherichia coli.

Researchers measured the antibacterial action of vinegar depended to:

• presence of sodium chloride (the common salt) and
• temperature

When scientists used 2.5% acetic acid (vinegar) at 20°C, they had to wait 739 min for the inactivation of pathogens.

This time shortened to 5.27 min by just adding 5% sodium chloride (salt).

Amazing…Just by adding salt, the time shortened to 1/140.

The results were even more astonishing when scientists used warm water.

Only with the use of 2.5% vinegar and warm water at 40 ^oC, the inactivation time was just 14.4 min. Less than a quarter of an hour…

What happened when scientists combined vinegar, salt, and warm water?

The inactivation time was only 0.89 min… Less than a minute…

From Tools For Survivial:

Prevention—What You Can Do

• Distance yourself from or avoid people and crowds. If you must go out, stay at least six feet away from individuals.
• Wash your hands for at least 30 seconds using soap and water frequently, but especially after using the bathroom, before cooking, and after shopping, opening doors, touching elevator button and grocery carts.
• Don’t panic or buy into the hysteria. Stay vigilant and research. The info being disseminated in the beginning is usually wrong.
• Get vaccinated.
• Self-quarantine.
• Cover your mouth when you cough or sneeze—preferably into your arm or elbow, not your hand.
• Wash your sheets and pillowcases every few days in hot water.
• Germs can live on surfaces for days. Disinfect surfaces regularly with bleach. Wipe down your desk, door knobs, handles, light switches, and elevator buttons at the office regularly with cleaning wipes.
• Heed the warning. Pay attention to advisories and take precaution. It is better to be safe than sorry. Stay inside if you must—you and others can spread disease without feeling sick or showing symptoms.
• Do not go to the hospital unless it is an emergency. Medical resources will deplete. Hospitals and doctor’s offices are hot beds of sickness. If you can, take advantage of your insurance’s call in service if available.

• Coronavirus Tech Handbook - provides a space for technologists, civic organisations, public & private institutions, researchers and specialists of all kinds to collaborate on a rapid and sophisticated response to the coronavirus outbreak and subsequent impacts. It is a quickly evolving resource with thousands of active expert contributors.
• FireMountain - links for information
• Flight Info - The flights have been found to have a passenger confirmed to have COVID-19.
• HealthLinkBC - Coronavirus disease (COVID-19) also known as 2019-nCov, originated from Wuhan, China, but has spread to a number of countries including to Canada. The risk to British Columbians remains low.
• COVID-19 projects looking for volunteers - These projects were posted by the community. Volunteer yourself or create a new one.
• FluTrackers - tracking Infectious Diseases since 2006
• Coronavirus COVID-19 Global Cases by the Center for Systems Science and Engineering (CSSE) at Johns Hopkins University (JHU)
• Johns Hopkins University (JHU) - better link to the map
• WorldOMeter - COVID-19 Coronavirus Outbreak
• The Prepared - If you’re worried about the SARS-COV-2 coronavirus outbreak or feel unprepared, this guide is for you. Experts explain what you should do to get ready, how to protect yourself, what researchers believe are the likely scenarios going forward, and the latest fact-checked news.
• Imperial College COVID-19 Response Team - Impact of non-pharmaceutical interventions (NPIs) to reduce COVID-19 mortality and healthcare demand - Here we present the results of epidemiological modelling which has informed policy making in the UK and other countries in recent weeks. In the absence of a COVID-19 vaccine, we assess the potential role of a number of public health measures –so-called non-pharmaceutical interventions (NPIs) – aimed at reducing contact rates in the population and thereby reducing transmission of the virus.
• Italian town's experiment leads to no new coronavirus cases in almost a week - Vò, a town of 3,300 just outside Venice, was part of an experiment that involved aggressive testing and quarantine measures. Every single resident was tested for coronavirus in late February when Northern Italy was first rocked by the outbreak, and three percent of inhabitants were found to be carrying the virus.
• TRSA - COVID-19 resources webpage for TRSA members in the linen, uniform and facility services industry.
• European Centre for Disease Prevention and Control - Preparedness planning is essential in order to respond effectively to outbreaks and epidemics. Sharing and aligning activities at European and international level in the area of public health emergency preparedness adds value to the efforts of single countries to strengthen their capacities and ensure coordinated and effective support when faced with cross-border health threats.
• Persistent Defenses Against the Wuhan Virus - by Howard Philip - Presented here for your consideration is a set of simple self-help measures you can implement to dramatically improve your chances of avoiding the deadly Wuhan virus, ranging from behavioral adjustments to the application of readily available materials and chemicals - real or fake?
• Federal Reserve Bank of New York - Coronavirus Resource Center - We have created this resource center where individuals, businesses, and non-profits can find out what’s available to them at the federal, state, and city level. This hub will be regularly updated to connect our communities with the necessary resources.
• GitHub repo for Wall Street Bets as they analyze the failures resulting from the virus.
• Genomic epidemiology of novel coronavirus - provides regular updates of virus evolution
• Coronavirus: Guidance for Better Mental Health - Self-care is vital, and it’s also important to try and reduce the stress for ourselves and others around us.

From the debian-boot mailing list:

 * pkgsel:
    - Ensure tasksel is installed, regardless of its priority.
    - Add preseedable pkgsel/run_tasksel debconf template, making it
      possible (by setting it to false) to skip tasksel entirely
      (installation and prompt), while still benefiting from other
      pkgsel features.
 * preseed:
    - Update auto-install/defaultroot, replacing buster with bullseye.

From a networking list serve:

Question:

Can anyone suggest tools, techniques and helpful contacts for backtracking spoofed packets? At the moment someone is forging TCP syns from my address block. I'm getting the syn/ack and icmp unreachable backscatter. Enough that my service provider briefly classified it a DDOS. I'd love to find the culprit.

Response:

It's not complete, but if you're receiving the ICMP net/port unreachable backscatter it should include a portion of the original packet. This might provide some insight into the TTL left on TCP the packet when it reached its destination which could provide a rough radius that you would need to look at. Also, if the TTL is constant it would support the idea that one or few hosts are spoofing your address block, but if the TTL varies widely it might indicate that many bots are spoofing your address block.

You might check looking glass tools or something like https://radar.qrator.net to see if someone is not only spoofing your address range, but has gone farther and has hijacked it.

The country code is not read from ACPI but from the EEPROM of the WiFi-card (0x0 "World Regulatory Domain" by default).

How to Build your Own Wireless Router (Part 3) - kernel requires code patch to enable 5GHz operations.

ath10k locks to regulatory domain US on ACPI platforms

• My Hard Drive Died - primary goal is to provide you with the data recovery knowledge and tools you need – whether it be our free videos and content, or our structured training (seated classes, distance learning or specialized).
• Resource Public Key Infrastructure (RPKI), the community-driven technology based on open standards that is aimed at making Internet routing more secure

Quite some ago, there was a discussion around [ovs-dev] Creating a libopenvswitch-dev package, back in 2016. Since then libraries have been updated for C++ inclusion, plus other improvements.

From somewhere, I don't have the reference, maybe my own blog, but since I have this in a note on my desktop, I'll include it here:

• Build a string formatted as the “ovs-ofctl” command would do, for example “table=1,cookie=0xdeadbeef,in_port=1,actions=resubmit(,2)”
• Pass this to parser_ofp_flow_mod_str(). The parser will magically parse the string in to a rich struct.
• Pass the struct to ofputil_encode_flow_mod(). This returns a struct with a serialized OpenFlow message buffer.
• Send this buffer on the wire either via a socket you manage yourself or let OpenVswitch do it for you.

From Phoronix - Linux 5.6 To Bring FQ-PIE Packet Scheduler To Help Fight Bufferbloat, there are some example configurations for using different buffering mechanisms (Implementing the Flow Queue PIE AQM in the Linux Kernel).

For wireless clients:

net.core.default_qdisc=fq
net.ipv4.tcp_congestion_control = bbr

and fq_codel (codel) is better suited for router.

Another possibility:

I had pretty amazing results with cake. I prefer it over fq_codel and it is now part of main line since 4.19.

Cake - Common Applications Kept Enhanced

In the past the internet would just grind to a halt when the Apple devices started cloud syncing. They would totally swamp the outgoing bandwidth. Now nobody notices when an Apple device is syncing.

Open firmware for small routers for congestion management:

The OpenWrt issue with 4MB has to do with using newer kernels. For those devices, DD-WRT is a better bet (still on kernel 3.10).

Overheard on a mail delivery email list:

What we do is FAR from Binary.

Heck, sometimes it feels like the square root of -1 is involved somehow.

An extract from bug #949655 at bugs.debian.org:

I finally found on iPXE website[1] a link to detailed examples, including one[2] to boot pxelinux. It works perfectly with di-netboot-assistant:

#!ipxe
dhcp
set 210:string tftp://my_server/d-i/n-a/
chain ${210:string}pxelinux.0

For those who did not know (like me ), 210 is a standard DHCP option called "path prefix"[3].

• [1]extensive ipxe menu example
• [2]menu.ixpe file
• [3]bootp dhcp parameters