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#1 2019-01-13 09:18:43

johnraff
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From: Nagoya, Japan
Registered: 2015-09-09
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Useful links to docs and tutorials

This thread is for those online docs that you've found useful or enlightening, or that explained something you didn't previously understand properly, or anyway that you think is worth preserving for others, or possibly might want to refer to in the future without having to search the whole forum for a certain link you found a year ago...

Please add a bit of info about why it's so useful, not just a plain link!

Anyway, here's one I've just read about mounting permissions and polkit, which goes in to the whole topic quite thoroughly:
http://smcv.pseudorandom.co.uk/2015/why_polkit/

Summary

   

  • Kernel-based permission checks are not sufficiently fine-grained to be able to express some quite reasonable security policies

  • Fine-grained access control needs domain-specific understanding

  • The kernel doesn't have that information (and neither does dbus-daemon)

  • The privileged service that does the domain-specific thing can provide the domain-specific understanding to turn the request into an action

  • polkit evaluates a configurable policy to determine whether privileged services should carry out requested actions

Last edited by johnraff (2019-01-13 09:20:13)


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#2 2019-01-13 13:23:52

S7.L
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Registered: 2018-09-16
Posts: 338

Re: Useful links to docs and tutorials

I cant remember the exact place that got me out of trouble on the internet now but i had used cfdisk from a live session to resize a multiboot partition, bad idea. So it involved booting to the live session again and using learning various fsck tools in linux because the partition sda5 now had inconsistency in the block sectors and it would not boot.

The only method that fixed this was to use resize2fs.

First search for a backup block with maybe this ..

dumpe2fs /dev/sda5 | grep -i superblock

Not really a how to this thread so i will end it there, it pays to read up on file system recovery methods such as fsck, mke2fs, dumpe2fs, resize2fs etc..

https://www.systutorials.com/docs/linux … resize2fs/

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#3 2019-01-13 17:14:41

Bearded_Blunder
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Registered: 2015-09-29
Posts: 730

Re: Useful links to docs and tutorials

When troubleshooting old, oddball, and otherwise cranky hardware that's refusing to boot properly, and you want to find the kernel parameter to get shot of the error:

This is the resource:
https://www.kernel.org/doc/html/v4.15/a … eters.html

Also useful to get rid of errors that go past but don't stop you booting, but still annoy you.

Rest of the document is also very useful, especially if you ever have a need to compile a custom or really new kernel.


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#4 2019-01-13 17:22:32

ohnonot
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Registered: 2015-09-29
Posts: 5,568

Re: Useful links to docs and tutorials

^ choose your kernel version here: https://www.kernel.org/doc/html/
one can also use this: https://github.com/torvalds/linux/blob/ … meters.txt - apparently always the current, newest git version.


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#5 2019-04-28 07:56:13

johnraff
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From: Nagoya, Japan
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Re: Useful links to docs and tutorials

An overview of Secure Boot in Debian
https://debamax.com/blog/2019/04/19/an- … in-debian/

(Put here so I can read it later.)


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#6 2019-05-21 04:03:50

johnraff
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From: Nagoya, Japan
Registered: 2015-09-09
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Re: Useful links to docs and tutorials

Upgrades from Debian 9 (stretch)

A guide to upgrading from Stretch to Buster, from the work-in-progress Buster release notes:
https://www.debian.org/releases/buster/ … ng.en.html

This might be useful soon.


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#7 2019-06-29 12:20:39

clusterF
Member
Registered: 2019-05-07
Posts: 539

Re: Useful links to docs and tutorials

https://wiki.archlinux.org/index.php/Ex … encryption

Im using this on archlinux and it is a very ingenious EXT4 file based encryption method.

Im not sure what kernel this was introduced in, having a look see now as it might not be relevant to debian stable.

Introduced in kernel 4.1 so all good.

https://blog.quarkslab.com/a-glimpse-of … ption.html

Last edited by clusterF (2019-06-29 12:29:27)

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#8 2019-06-30 06:25:18

ohnonot
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Registered: 2015-09-29
Posts: 5,568

Re: Useful links to docs and tutorials

^ very nice feature.
It means I'll be needing one less software soon.


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#9 2019-10-27 11:27:07

clusterF
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Registered: 2019-05-07
Posts: 539

Re: Useful links to docs and tutorials

This is a good resource on shell scripting. Really goes into great detail with examples and practical lessons. I found the whole section on writing shell scripts enlightening, however the section on Keyboard Input and Arithmetic was an eye opener.

http://linuxcommand.org/index.php

Last edited by clusterF (2019-10-27 11:39:20)

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#10 2019-10-27 12:21:32

ohnonot
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Registered: 2015-09-29
Posts: 5,568

Re: Useful links to docs and tutorials

clusterF wrote:

https://wiki.archlinux.org/index.php/Ex … encryption

Im using this on archlinux and it is a very ingenious EXT4 file based encryption method.

Im not sure what kernel this was introduced in, having a look see now as it might not be relevant to debian stable.

Introduced in kernel 4.1 so all good.

https://blog.quarkslab.com/a-glimpse-of … ption.html

I totally forgot about this!
https://wiki.archlinux.org/index.php/Fscrypt
Seems a little complex - I hope I won't forget about it again - it's not a high priority.


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#11 2019-10-27 13:11:32

clusterF
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Registered: 2019-05-07
Posts: 539

Re: Useful links to docs and tutorials

^ That looks like a new entry in the arch wiki? Covers f2fs file system too. Interesting, thanks for sharing.

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#12 2019-12-18 10:11:38

clusterF
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Registered: 2019-05-07
Posts: 539

Re: Useful links to docs and tutorials

I just came across a program called gocryptfs and found this tutorial or sorts.

https://sudomakemeablog.wordpress.com/2 … eat-sheet/

This is perfect (imo) if you dont want whole system encryption and just file/directory encryption.

You could fire off a startup script like so to automate things a little better from either openbox/autostart or .xinitrc or whatever you use to autostart programs.

call it gocrypt.sh or something that doesn't clash with gocryptfs.

#!/usr/bin/env bash
echo "Enter your gocryptfs password"
if      mkdir /tmp/decrypted; then
        xterm -e "bash -c 'gocryptfs encrypted /tmp/decrypted;$SHELL'"
fi

or just a one liner.

xterm -e "bash -c 'echo Enter your gocryptfs password && mkdir /tmp/decrypted && gocryptfs encrypted /tmp/decrypted;$SHELL'"

Last edited by clusterF (2019-12-18 11:56:59)

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#13 2020-07-23 05:11:25

johnraff
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From: Nagoya, Japan
Registered: 2015-09-09
Posts: 8,332
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Re: Useful links to docs and tutorials

Trying to figure out why a script running on dash wasn't running an EXIT trap on Ctrl+C (not an unreasonable thing to want). Much internet searching, finally found a workaround, but in the process ran into a couple of deep, deep webpages with huge amounts of info about systems and shells I'd had no idea even existed.

A humbling experience.

Portable Shell Programming
For userland utilities on BunsenLabs, or anyway Debian, bash is much more writer-friendly than a basic POSIX shell. Arrays, process substitution and feature after feature...
But if you're writing a system script, quite likely going to be run as root, then it had better be reliable and predictable, and not change its behaviour if someone runs it on a different system, or after a package upgrade. For that, you're better off with a #!/bin/sh shebang and trying to make the whole thing as POSIX-compliant as you can. Not always that easy (shellcheck and checkbashisms can help), but this page has a huge amount of things you can do to make your scripts as shell-friendly as possible: https://www.gnu.org/software/autoconf/m … Shell.html
Written in 2012, and some of it we can thankfully forget about in 2020, but still monumental.
Example sub-page: https://www.gnu.org/software/autoconf/m … ltins.html

arbitrary unix stuff
I haven't even begun to read this yet, but it looks to be in the same league (and written in 2009).
Good read for a Sunday afternoon. https://www.in-ulm.de/~mascheck/various/

Example hint on Useful use of cat:

create text files without editor

  cat > textfile

then typing plain text and closing with EOF (aka <ctrl-d>) was the quickest way for me to create text files on systems running in some rescue mode.


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#14 2020-09-19 07:14:05

johnraff
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From: Nagoya, Japan
Registered: 2015-09-09
Posts: 8,332
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Re: Useful links to docs and tutorials

Debian Installer Components

This is quite a good description of the different parts of the Debian Installer:
https://www.debian.org/releases/stable/ … 03.en.html


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#15 2021-03-08 04:36:51

johnraff
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From: Nagoya, Japan
Registered: 2015-09-09
Posts: 8,332
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Re: Useful links to docs and tutorials

freedesktop.org Interoperability specifications

In one place, links to all the XDG standards:
https://www.freedesktop.org/wiki/Specifications/


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#16 2021-03-08 04:43:28

johnraff
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From: Nagoya, Japan
Registered: 2015-09-09
Posts: 8,332
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Re: Useful links to docs and tutorials

Deprecated Linux networking commands and their modern replacements

Detailed list:
https://dougvitale.wordpress.com/2011/1 … lacements/

These two networking articles by the same author look useful too:
https://dougvitale.wordpress.com/2011/1 … ty-part-1/
https://dougvitale.wordpress.com/2011/1 … -commands/
But refer to the first link for the up-to-date commands (even though ~10 years old!).

User in Debian-User ML wrote:

Well, it's been about a decade since that was written but not much has
changed. One issue is, ifconfig shows only one address per interface
while you can today have more. I was bitten by this last year, I
borrowed a port from what I thought was a co-worker's desktop
switch. Turns out it was actually a router with the end result that my
dev board somehow ended up with two IP addresses, one from that router
and another from the general network. Connections didn't work that well
but ifconfig showed everything was just fine and I had the expected ip
address.

Finally, ip addr showed the actual situation and ip addr del mumble and
some other commands fixed my connectivity issues.

Last edited by johnraff (2021-03-09 08:01:35)


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#17 2021-07-03 06:15:58

johnraff
nullglob
From: Nagoya, Japan
Registered: 2015-09-09
Posts: 8,332
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Re: Useful links to docs and tutorials

You're never too old to learn something. smile

Obsolete and deprecated syntax from the bash hacker's wiki:
https://wiki.bash-hackers.org/scripting/obsolete

That led on to Bash Pitfalls from Greg Wooledge's wiki:
http://mywiki.wooledge.org/BashPitfalls
Also full of tricky stuff I only half-understood.

Both worth a read IMO.


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#18 2021-07-03 06:19:30

johnraff
nullglob
From: Nagoya, Japan
Registered: 2015-09-09
Posts: 8,332
Website

Re: Useful links to docs and tutorials

How to Report Bugs Effectively
https://www.chiark.greenend.org.uk/~sgtatham/bugs.html
The title says it.

Here's a good quote:

When something goes wrong, immediately stop doing anything.


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#19 2021-07-08 05:05:07

johnraff
nullglob
From: Nagoya, Japan
Registered: 2015-09-09
Posts: 8,332
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Re: Useful links to docs and tutorials

HOWTO set DPI in Xorg

A while ago some of us got into a discussion of dpi as a distracting sidebar to someone's screen display size issues:
https://forums.bunsenlabs.org/viewtopic.php?id=7315

It is annoying, and this article expands a bit:
https://linuxreviews.org/HOWTO_set_DPI_in_Xorg

It used to be possible to configure font DPI in GNOME but that was a feature for people with poor eye-sight and GNOME developers hate actually user-friendly features so it had to go.


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#20 2021-07-08 08:18:41

ohnonot
...again
Registered: 2015-09-29
Posts: 5,568

Re: Useful links to docs and tutorials

johnraff wrote:

A while ago some of us got into a discussion of dpi as a distracting sidebar to someone's screen display size issues:
https://forums.bunsenlabs.org/viewtopic.php?id=7315

There's a link to a very old bug report in there somewhere, very confusing. Essentially it sounds like DE developers decided to ignore Xorg's DPI settings at some point, and therefore Xorg decided to ignore autodetection...?!

johnraff wrote:

It is annoying, and this article expands a bit:
https://linuxreviews.org/HOWTO_set_DPI_in_Xorg

I don't rightly see anything annoying in there (apart from obvious rant about GNOME f*ckery).
But it makes me wonder what will happen if I remove my manual settings again and just see what Xorg autodetects...

Last edited by ohnonot (2021-07-08 08:19:14)


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#21 2021-07-08 10:04:47

johnraff
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From: Nagoya, Japan
Registered: 2015-09-09
Posts: 8,332
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Re: Useful links to docs and tutorials

^I meant dealing with dpi was annoying, and the article expanded a bit on that. Not that the article itself was annoying.

It seems X is perfectly aware of both display dimensions and pixels, but chooses not to interpret them.


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#22 2021-07-08 18:11:39

jeffreyC
Member
Registered: 2019-09-07
Posts: 68

Re: Useful links to docs and tutorials

ohnonot wrote:
johnraff wrote:

A while ago some of us got into a discussion of dpi as a distracting sidebar to someone's screen display size issues:
https://forums.bunsenlabs.org/viewtopic.php?id=7315

There's a link to a very old bug report in there somewhere, very confusing. Essentially it sounds like DE developers decided to ignore Xorg's DPI settings at some point, and therefore Xorg decided to ignore autodetection...?!

johnraff wrote:

It is annoying, and this article expands a bit:
https://linuxreviews.org/HOWTO_set_DPI_in_Xorg

I don't rightly see anything annoying in there (apart from obvious rant about GNOME f*ckery).
But it makes me wonder what will happen if I remove my manual settings again and just see what Xorg autodetects...

What happened is that the Xorg devs decided to be 'bug compatible' with Windows and set the DPI at 96 no matter what the display said.
Microsoft removed the bug with the release of Windows 7.
Xorg still over a decade later declares it NOTABUG and WONTFIX.

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#23 2021-07-23 10:58:23

ohnonot
...again
Registered: 2015-09-29
Posts: 5,568

Re: Useful links to docs and tutorials

^ that sucks for sure.
Anyhow, it's possible to set correct DPI (or manipulate it generally) with the help of the mentioned article.


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#24 2021-09-19 18:49:29

NightOwl
Member
From: Netherlands
Registered: 2018-03-12
Posts: 8

Re: Useful links to docs and tutorials

Here is a nice little article from itsfoss explaining the difference between the

apt

and

apt-get

commands used when installing and updating packages.

Difference between apt & apt-get

Thought it might be something interesting to read for a newer Linux user to know what the actual difference is smile

EDIT : This one might be good too
SSH Academy - Command

Last edited by NightOwl (2021-09-19 20:12:18)

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