Yeah it was wild, but I suspect few orgs do things that way any more.

Salmon reversing aid.

You mean in the context of high availability?

tl;dr: It’s to test if the cluster fail-over configuration is working properly.

So this was before things like Kubernetes or Terraform were a thing, so had to be done by the operating system itself. The simplest HA cluster is made of two nodes, one in “active node”, the other “passive”. The active node does all the work, and the passive node just keeps its data synchronised with the active node. I used to use DRBD for this, which is a system for copying writes to the active node over a network link to the passive node. That only gives you a “second, up-to-date copy” which is not that useful on its own - you also need a way to automatically switch over to using the passive node if the active one “dies”, and for that I used to use “heartbeat”, which simply passes packets back and forth between the two cluster members - ping-pong style - and if the passive node notices that the active node hasn’t sent its scheduled packet for, say, 10 seconds, it cuts it off the current active node (kills it), and promotes itself to the active role, thus preserving the service. Killing the “other node” is necessary to stop data corruption or user requests going to a node that can’t actually service them, and is called STONITH - Shoot The Other Node In The Head. STONITH can involve an electronically controlled switch, which literally cuts off power to the “other” node, or can isolate it on the network, by shutting down its network ports on the switch, or in a VM setup, sending a notification to the hypervisor to kill the VM.

The reason you need to be able to kill the kernel on the active node, is that when you manually shut down the active node, it automatically informs the passive node that it’s going down, known as an “orderly fail-over”, and you’re not actually testing if the heartbeat fail-over works, you’re just testing an orderly fail-over. Killing the active node’s kernel tests that the passive node is properly configured to take over during a catastrophic failure of the active node. You can watch the heartbeat status go from “up” to “down”, and then see the passive node decide to take over, promote itself and bring up its services, and begin processing requests.

To make sure it’s all working, you need to test orderly fail-overs first, from both nodes, then test disorderly fail-overs both ways, by using the kernel gun on the active node.

Things moved on from Heartbeat-based HA clusters to multimode clusters managed by Corosync and other software, enabling other strategies to be employed. This was eventually supplanted by “orchestration” systems like Kubernetes, and proprietary Virtual Cloud systems that move this functionality to the platform rather than the operating system.

Nah man. “kill” doesn’t shut the system down quickly. This is the “instant death” way - the kernel reset gun - no shutdown scripts, no disk sync, just reset to BIOS boot sequence, instantly:

As root:

echo 1 > /proc/sys/kernel/sysrq

echo b > /proc/sysrq-trigger

If you change out the “b” in the second command for “o” it will just halt the kernel instead of rebooting. Still switched on, but the system is doing absolutely nothing.

I used to use this trick all the time to test high availability server clusters.

Sounds great, look forward to seeing that. After using it a bit more, another thing occurred to me - there’s no way to open arbitrary files. I don’t use MarkDown for “just notes” or “just one thing”, I keep markdown files all over the place. I had set the repository directory to be that of my blog posts during first run, but then I can’t open things in my notes directory or documents folder, and I can’t see anywhere in the settings dialogue to change it. Am I missing something?

Yeah “but not as annoying” lol. No idea what you mean about jeeps: I’m in the UK, and not a car enthusiast either.

Seems quite good - I’ve tried a LOT of MarkDown editors over the years, but until quite recently, I’d stuck with Zettlr for a long time. I’ve recently reinstalled my laptop, which made me look for alternatives to some software, and I’ve been playing round with MarkText for the last few days, which seems nice.

HelixNotes is definitely good - if I had to drop MarkText, I think I could get on well with it. I like that they have a debian repository, so I can keep it updated with the usual system update software. I downloaded the AppImage as a quick test, but it didn’t work because it was compiled against an old version of glibc.

The only thing I don’t like so far is the format toolbar is at the bottom of the editor screen, and I haven’t found a way to move it.

You’re quite right, Ozone is actually O₃, I got that wrong. I should have looked it up, but I didn’t, hence the error. I’m so sorry I mislead you - can you forgive me? Ozone is actually very interesting - did you know there is a layer of the upper atmosphere known as The Ozone Layer, and that it has a hole in it? Also, Ozone is sometimes produced by chemical reactions and electrical arcs - it has a distinctive, Ozoney smell. As you also made mistakes, I think we are now even - have you ever considered taking up a career as a Large Language Model?

What about Microsoft Bob? Doesn’t that count as their first attempt?

Just wait until LLMs are used to design most of them - they will be distinctively average.

I usually do that too, but this time round I’ve really not had the spoons. Had the “Red Letter” yesterday - “we’re sending in the heavies”. I still CBA - send 'em. We don’t have a telly and we don’t watch any telly via the web - we HATE TV. I don’t even watch any U-tubers regularly. Been this way for >20 years.

This diagram is wrong on so many levels. Ozone is “charged Oxygen” (O1 rather than the usual O2) so it’s saying you get Ozone out of the Hydrogen side. The bubbles are forming in a place where they can’t get to the output vents, so the accumulating gases would slowly force the water level in the inner chamber down, and thus up through the vents. It’s pretty shit. Is it AI slop?

NPM is not a Linux thing - it’s to do with web applications, so it works on Windoze and Mac too.

I learnt to “type” when I was at school, programming a Commodore Vic-20. I thought I was quite fast, but what I had really learnt was just the key combos for common words. It’s what most people who have never learnt properly before do, and it’s called “point and poke”. You don’t realise the extra effort you’re putting in, and the mistakes you’re making (overuse of the backspace key) and so on.

When I went to college at 16 (UK) to study computer science, we had the option of learning touch typing. We all thought we were pretty good at typing, but afterwards, we’d all doubled our typing speed (or more) and increased our accuracy by 10x. We learnt on proper electric golfball typewriters, and as we got better, we all noticed that code entry got a lot faster. The thing that is affected most, though, is typing up from notes or printed copy - because you don’t have to keep looking away from the source, back to the keyboard and screen, you can be much quicker. Also, typing your thoughts is much faster as you are not having to split your attention between the thoughts and the keyboard - what you think just appears on the screen without having to spend mental effort on typing.

That’s fair. I’m thankful for your perspective - food for thought. You’re right I’ve not seen that section of society from that angle, though I have a sibling who went through addiction. They were a “functional addict” and were working throughout, so I’m aware of that angle, at least. That was all decades ago now, though their partner had a relapse after an operation when they were given opiate painkillers. I think you’re being hard on yourself though - and I don’t know your circumstances, so I don’t know how you got into that mess, but although it’s easy for outsiders to frame addiction as a personal failure, I think the circumstances that led to that path are often ignored. I see such problems as a systemic failure, rather than a personal one. I’m glad you got clean of the class A’s, it’s no small achievement, and I hope you’re making progress with the rest - though I understand that Nicotine is perhaps the hardest of all to kick. I do think you have a bit of survivor bias there, though. One thing I’ve learnt recently, is that not everyone has the same abilities to get through - I know you’ve seen chancers, and you managed to get through, but I don’t think it’s true that everybody could have taken your path.

For myself, I’m getting help from the CAB, so we’ll see where that goes. I start 1-to-1 support next week with the local “Autism Hub” which is an entirely new thing to me - I’ve never “been in the system” before, so it’s an “interesting” learning curve. I have ups and downs - the past few days I have been far better, but I keep relapsing due to factors outside of my control - mainly caused by said system. I just need the time and space to recover properly, but I don’t know if I’m going to get it. Purely “mental health” things are something this system seems hell bent on denying, so I’m expecting a continuing struggle. I have no choice but to push on.

It didn’t quite work like that. They used to arrive boxed in batches. The keyboards were worth about £100 back then - so would be worth a lot more in today’s money - and they were looked after with care whilst in transit. It was the end users (in offices) that put the gunk there.

Can confirm. Back at the beginning of my IT career (mid 1980’s), I worked as a temp for a computer manufacturer in their refurb repairs department. In those days, kit was so expensive that everything got repaired if it went wrong, and one of my jobs was repairing keyboards - PC keyboards, and dumb terminal ones - and the first part of the process was stripping and cleaning them. There was a lot more room for crumbs and dust back then, too, and man did they get full. Crumbs, staples, paper clips, hair grips, all sorts. I had literal mould growing in some of them. I remember the ones coming in from Italy were the worst for that for some reason.

Well, it depends what you call spam, how well known your server is (are your email addresses spread far and wide on the web or only known to a couple of people) but a lot of spam is automated and algorithmic, so most servers will be showered with speculative mail addressed to likely mailboxes - which your server still has to process, if only to bounce the message; if you have antispam measures, your server can just drop the connection when it detects a spammy sender (e.g. from an address on a black or greylist). I’m not currently running any mail servers, but a few years back when I did, I used to get about 80% spam incoming.

The list is immense, and I didn’t want to clutter my post with all the details. So just listing off things that spring to mind (because I don’t know what OP doesn’t know):

• Choosing an MTA - sendmail, postfix, exim, etc. and why you might choose one over the others
• Firewall settings
• Software/package management on your chosen distro
• Learning about DNS:
  • Host it - yourself via BIND
  • Or via a DNS service provider
  • DNS record types
    • Domains
    • Subdomains
    • A records/CNAMEs
    • MX records
    • Mail authority records - SPF’s
    • Mail encryption records - DKIM
• Spam filtering, anti-virus
• Learning how to configure your MTA, which requires learning:
  • the configuration file language your MTA uses
  • what all the options mean and what they do
  • what the bare minimum options are to get up and running
  • how to make sure your configuration is secure and won’t be exploitable by bad actors
  • how mail really gets delivered
  • how to setup secure smtp
  • how to set up SPFs
  • troubleshooting why GMAIL or Microsoft won’t accept your mail
  • troubleshooting why GMAIL or Microsoft have stopped accepting your mail
  • dealing with blacklists/greylists when someone sends too many messages, or something that “looks too spammy”
• Mail hosting pitfalls
  • Being an open relay
  • Rate limiting
  • Reputation management
  • Vulnerabilities that let a hacker take over your server
  • Resource management - disk, memory, processes, queues, etc.
  • Downtime when you need to do updates
  • Downtime if you change your DNS configuration

I’ve definitely missed some stuff, and each of those things requires knowing other stuff too, so you can see that it’s really a pretty deep subject. This is precisely why not many people self-host email themselves these days - the big guys have made it harder and harder to do so, in the name of eradicating spam, which they themselves are the biggest vectors for.