L
Lone Sysadmin
lonesysadmin.net · Personal blog · on HN since 2009
A system administrator writes practical notes on Linux, VMware, SSH, hardware troubleshooting and IT operations.
What HN saysHN links it for practical sysadmin tips, such as SSH escape sequences to kill dead sessions and tuning Linux disk caching.
15HN people shared it
5linked it in comments
11stories submitted
576story points
1 year agolast shared
2009people per year2026
Most-shared posts
- 1SSH Escape Sequences4 people · 403 points · first shared 2014 · 82 comments on HN
- 2Better linux disk caching performance vm dirty ratio2 people · first shared 2024
- 3Out-Of-Office Messages Are a Security Risk1 people · 161 points · first shared 2019 · 88 comments on HN
- 4How to Troubleshoot Unreliable or Malfunctioning Hardware1 people · 4 points · first shared 2018 · discussion on HN
- 5Three Thoughts on the Nutanix and StorageReview Situation1 people · 2 points · first shared 2015 · discussion on HN
- 6End Anonymous Conference Feedback1 people · 1 points · first shared 2019 · discussion on HN
- 7How to Write a Good Script1 people · 1 points · first shared 2009 · discussion on HN
- 8Big Trouble in Little Changes1 people · 1 points · first shared 2016 · discussion on HN
- 9Dear Microsoft: One Central Update Framework1 people · 1 points · first shared 2011 · discussion on HN
- 10Advice on Downgrading Adobe Flash1 people · 1 points · first shared 2017 · 1 comments on HN
- 11The Canonical List of Hypervisors That Suck1 people · 1 points · first shared 2015 · discussion on HN
- 12Heisenberg monitoring1 people · first shared 2024
What HN people wrote when they linked it
ahazred8ta · 2024-05-30
The ACTUAL Heisenberg uncertainty principle does not have any effect on software, or on normal computer hardware such as cpus. The problem where an error goes away when you try to look for it is unrelated to any actual quantum effect. Bug analysts are only using the word 'Heisenberg' as a metaphor. It only confuses people. Please stick to 'observer effect' instead.
https://en.m.wikipedia.org/wiki/Observer_effect_(information_technolog…
https://lonesysadmin.net/2010/01/05/heisenberg-monitoring/
https://en.m.wikipedia.org/wiki/Heisenbug
Tyrannosaur · 2024-03-25
It's possible you were seeing another problem, but this issue is more likely to appear with a faster network connection, because the network transfer happens faster than the disk writes.
You can confirm by watching /proc/meminfo and watching the Dirty and Writeback numbers.
Changing up the vm.dirty* settings can help as described here:
https://lonesysadmin.net/2013/12/22/better-linux-disk-caching-performa…
jwilk · 2017-10-24
LargoLasskhyfv · 2025-07-21
Depends on your usage patterns. On 8GB I gave it (ZRAM) between 512MB to 768MB RAM, and later on just using whatever values for the relevant sysctls AntiX was using(or their scripts created dynamically during setup/startup) at the time. It isn't just vm.swappiness, there are others, and they changed, or got removed, and replaced by others, over the years. And all of them sort of interwoven, influencing each other via what's happening in vm-subsystem. Can have bad feedback loops if you do it wrong, and be counterproductive. So you have to experiment, and measure with different settings, for what you're running.
Where measure can be anything from htop/atop over https://github.com/cdown/psi-notify , to https://github.com/noiseonwires/memory-pressure and so on.
To understand what these sysctls are about, how they are related to each other, and to ZRAM, I'd recommend reading, or at least skimming https://chrisdown.name/2018/01/02/in-defence-of-swap.html , https://chrisdown.name/2019/07/18/linux-memory-management-at-scale.htm… , https://linuxblog.io/linux-performance-almost-always-add-swap-space , https://linuxblog.io/linux-performance-almost-always-add-swap-part2-zr… , https://linuxblog.io/linux-performance-no-swap-space , https://linuxblog.io/running-out-of-ram-linux-add-zram , https://github.com/ValveSoftware/SteamOS/issues/899 , https://lonesysadmin.net/2013/12/22/better-linux-disk-caching-performa… , https://github.com/CachyOS/CachyOS-Settings/pull/19 ,…
unconed · 2014-08-15
Formatting legacy stuff was always part of the deal, but at the same time, I was never interested in being able to host vim. Some people disagreed rather vocally.
One of the things I discovered was just how much legacy cruft is really around. Not just things like ANSI colors, but e.g. grotty syntax. It made no sense until I realized it was created for teletype printers... it underlines things by backspacing after every character and printing a "_". It bolds by backspacing and repeating the character. I had to parse this to support man pages, and I assume the default TTY still does too.
The other thing was that so much of Unix workflow really only works by accident. The fact that you can ssh + sudo + ssh + ... is because the pipes are too dumb to fuck it up. Take for example SSH escape sequences... [1] they only work on the first hop. The proper solution is out-of-band signaling.
From an architecture point of view, the whole termcaps / stdio thing is crazy. The Unix principle is supposed to be about simple agnostic composition, and yet most tools have to sniff out their environment in order to maintain this illusion. Text files are for people, not machines. And if you want to see a never ending discussion, just ask a bunch of greybeards how to write a shell script that can handle files with spaces in their name.
[1] http://lonesysadmin.net/2011/11/08/ssh-escape-sequences-aka-kill-dead-…