/dev/chat

8:47 AM

@Isaac yes, it’s a major mode, so we exited it as soon as we started talking about other topics and activated the corresponding major mode ;-)

@Biswapriyo that’s the text-mode installer, which is available on all platforms; I imagine it’s the default on arm64...

Biswapriyo

9:47 AM

@StephenKitt Is there any docs about how Debian CD/DVD images are made? For example, ArchLinux has archiso package. My GoogleFu does not work, it shows how to make bootable media.

Stephen Kitt

10:15 AM

@Biswapriyo see the debian-cd package and its documentation; wiki.debian.org/DebianCustomCD is also useful

Jeff Schaller

1:20 PM

@StephenKitt show-Google-fu-mode

Stephen Kitt

2:32 PM

@JeffSchaller still waiting to see some Google-fu :-P

Kusalananda

Two bash shell functions calling each other recursively (by mistake), one doing a curl request against our mail server's REST API. Server goes down. Oops. I thought bash had a maximum recursion depth... or it's been increased significantly "for convenience".

Jeff Schaller

@StephenKitt some say it has already happened

@Kusalananda Sorry to hear! Sounds like BASH-DOS v1.0? The mail server has been bashed?

Stephen Kitt

@JeffSchaller ah, right! no searching involved there though ;-)

Kusalananda

@JeffSchaller Yeah, had to extract our sysadmin from a meeting to get mail back up and running for 100+ users... He was ok with it tho.

Jeff Schaller

@StephenKitt (impressed whistle)

Isaac

2:45 PM

@StephenKitt So, it was show-Brain-fu-mode

Jeff Schaller

@Kusalananda being extracted from a meeting is usually a net-positive :)

Stephen Kitt

@Isaac hah yes

there was a running joke at one of my previous jobs that, assuming brains have finite storage capacity, at some point I would try to shove so much trivia into mine that I’d forget important stuff, like getting dressed before going to work

I fixed that by getting a job working from home

Jeff Schaller

lol

Stephen Kitt

(but I do get dressed before starting work)

Jeff Schaller

using technology to solve problems, I love it

Kusalananda

2:49 PM

@StephenKitt Happened to me. I put a V-neck t-shirt on back to front. Nobody mentioned anything. Noticed it when I looked myself in the mirror in the evening...

terdon

@StephenKitt always? Come on, be honest.

Stephen Kitt

@Kusalananda hah nice, I take you didn’t have a jersey or something on top of the t-shirt

terdon

I have been known to wear my underwear to a morning scrum meeting once or twice. Not more than that, I don't think, but sometimes I wake up just at the time of the meeting...

Stephen Kitt

@terdon yup, because I take my youngest daughter to school before work ;-)

terdon

Ah well, that will do it :)

Kusalananda

2:50 PM

@StephenKitt No, this was in the summer in the UK.

terdon

@terdon a USB device can also be a keyboard, a network interface, etc. (even if it doesn’t claim to be on the box). — Stephen Kitt 13 mins ago

@StephenKitt yes, of course, but malware can be loaded off of a CD just as easily as off of a USB drive, so what's the point in blocking USB devices while allowing arbitrary data to be loaded onto the machine via CD?

Stephen Kitt

@terdon in most setups you need to start a piece of software on the CD explicitly, don’t you?

terdon

@StephenKitt So? I'm the attacker, I can launch what I want.

But there are also many GUIs that will autorun CDs. Probably most, these days.

Stephen Kitt

@terdon if you’re in the system already, why do you need a CD?

terdon

@StephenKitt To bring in your attack tools?

Ah, you're thinking of users with no access to the system (as in "only" physical access, but no username/pass) who would use a usb attack device to get access?

Stephen Kitt

3:02 PM

@terdon yes, drop a USB stick in a car park

terdon

I was thinking of malicious users who already have user-level access and are trying to get more.

Stephen Kitt

@terdon right, run a password-cracking tool off a live CD for example

terdon

@StephenKitt There you go then, no USB access needed. You can simply boot off of the CD, so again, is there really much point in blocking USBs if you still allow CDs?

@StephenKitt heh, yes:

186

A: What is the danger of inserting and browsing an untrusted USB drive?

The worst that can happen is limited only by your attacker's imagination. If you're going to be paranoid, physically connecting pretty much any device to your system means it can be compromised. Doubly so if that device looks like a simple USB stick. What if it's this? Pictured above is the i...

Stephen Kitt

@terdon right, there are scenarios where CDs are dangerous in any case

e.g. even the basic one where a user puts a CD in, nothing happens, but then they reboot

terdon

yeah

Stephen Kitt

3:05 PM

one of my systems fails to boot if a USB floppy drive is connected to it

terdon

Which is why I'm confused at the idea that the OP there wants to block USBs but allow CDs. It just seems like locking the front door while leaving the window open.

Stephen Kitt

yes

if someone has physical access to your system you’ve lost anyway

unless it’s a Chromebook or a Mac maybe

Videonauth

4:07 PM

@StephenKitt And even then you have lost :)

I watched a documentation about how police forces get data off of android and apple devices (sadly in german) last week, no chance to keep your stuff safe.

Stephen Kitt

4:21 PM

@Videonauth even with encryption?

Videonauth

well so they stated in the video doku

not sure if you can trust that because RSA/AES etc is yet to be broken if my informations are correct

Stephen Kitt

well yes, that’s my assumption too

the advantage of Chromebooks and Macs is that they have meaningful trusted boot setups, so you know that your system hasn’t been tampered with, and that no one is reading your encryption passphrase as you type it

Videonauth

was a tv documentation, and still we live in a digital world they are still unable to manage a proper research

Stephen Kitt

sensational beats accurate every time

Videonauth

anyways here in germany and inUK they can jail you infinite if you refuse to give up your password

Stephen Kitt

4:26 PM

yes, there’s that too

Videonauth

nice fine anti terror law act which they now use on everyone

even if you simply stole some candy from a store they use that to get every bit of information about you including your DNA fingerprints etc

this is slowly getting ridiculous tho

Kusalananda

4:56 PM

OpenSSH 8.2 has FIDO support. At last I get to use that otherwise useless Yubi key for something!

terdon

5:19 PM

@Videonauth Eh, they don't need your password to get your DNA. And people are giving theirs out left, right and center anyway. That is the really crazy bit.

MyWrathAcademia

6:43 PM

Any experts in regular expressions here?

Jeff Schaller

@MyWrathAcademia there's a bunch on the site, if you have a question...?

MyWrathAcademia

I'm trying to perform search and replace on this string "Abbey Street E.2 Buckfast Street" with :s/[^ ]* [^ ] /Z/but I'm getting "ZStreet". Any idea how I can get "BuckFast Street"?

@JeffSchaller ^

Basically I want to match everything up to the second to last white space chatacter in that string

Jeff Schaller

@MyWrathAcademia I would recommend:

82

Q: Why does my regular expression work in X but not in Y?

I wrote a regular expression which works well in a certain program (grep, sed, awk, perl, python, ruby, ksh, bash, zsh, find, emacs, vi, vim, gedit, …). But when I use it in a different program (or on a different unix variant), it stops matching. Why?

I suspect you're running into * matching zero instances

(when you want 1-or-more)

MyWrathAcademia

What do you mean zero instances?

terdon

@MyWrathAcademia on what operating system, using what tool and what flavor of regular expressions? Why would you expect to get BuckFast Street if you are replacing with 'Z'?

Jeff Schaller

6:56 PM

[^ ]* says: match zero, 1, or more things that aren't a space

terdon

This is the sort of thing it would be good to explain in your question...

Jeff Schaller

matching zero things can be surprising, but is allowed

it's also something that can be nicely explain in a Q&A :)

terdon

$ echo foo | grep -q 'b*' && echo 'found!'
found!

MyWrathAcademia

Basically I want to match everything up to the second to last white space chatacter in that string

@terdon MacOs, using vim and zshell.

@terdon Oh sorry , tired eyes. I am hoping to replace with nothing i.e. an empty string

terdon

Replace what with nothing? See, this is why it is so hard to do in chat. We need to coax every little detail out of you. Why don't you post a question on the site, where you can explain what you are doing and then we can help you easily!

MyWrathAcademia

7:01 PM

So I want "Abbey Street E.2 Buckfast Street" with :s/[^ ]* [^ ] // to give me "BuckFast Street"

I will create a question now and link it here

terdon

$ echo "Abbey Street E.2 Buckfast Street" | sed -E 's/.* ([^ ]+ [^ ]+)$/\1/'
Buckfast Street

Something similar should presumably work in vim.

by the way, @MyWrathAcademia this site can be very useful for people trying to understand regular expressions: regex101.com

That would show you what you are actually matching.

MyWrathAcademia

@terdon @JeffSchaller unix.stackexchange.com/questions/568134/…

I have posted the question. Thanks

@terdon I havent been using the command line as much as I used to and I'm surprised how rusty I've become. I'm sure I could have done this months ago.

terdon

7:22 PM

@MyWrathAcademia Thanks. May I ask why you had tagged that with linux?

Also, you still have the same example there: you are replacing with Z for some reason.

And you describe something very different: " I'm trying to delete everything up to the second to last character," that would mean leaving only "et".

Anyway, I'll let one of the vimfidels answer this, I don't know how vim works.

MyWrathAcademia

@terdon Thanks for spotting mistakes. Tired eyes. I have addressed all your concerns (I hope)

Thank you

I would stick with sed if not for the fact that I have to run that command on on a file with 2000 lines of strings in a similar format as "Abbey Street E.2 Buckfast Street"

@terdon your command works using sed but not with vim. Why is this when both are using the substitute command?

Jeff Schaller

7:41 PM

This won't surprise very many people here, but I just used ed for a production change. One line in the file was too long for vi -- "The window is too small to display the current line."

(and I lack a 9974-character-wide terminal)

MyWrathAcademia

37 mins ago, by terdon

$ echo "Abbey Street E.2 Buckfast Street" | sed -E 's/.* ([^ ]+ [^ ]+)$/\1/'
Buckfast Street

@terdon Please help me undertand your solution:

Does . mean match any character. * mean up to. ([^ ]+ [^ ]+) mean group any non white space character up to a white space character (i.e. the [^ ]+ part in parentheses) and any non white space character up to a white space character (the second [^ }+ part in parentheses). Then $` means end of line. \1 means use the matched pattern? What does + mean here?

terdon

7:58 PM

@MyWrathAcademia I'm sorry, I don't have time to at the moment. I will try and post an answer when I get back if nobody has posted my solution.

MyWrathAcademia

@terdon its okay, I understand. I look forward to your answer. It helps to understand each component that makes up the argument passed to sed.

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