/dev/chat - 2017-07-11

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derobert

01:19

@FaheemMitha well, I mirrored rootfs and swap, both very much in use. So it's not that.

Faheem Mitha

01:49

@derobert But within the VM, correct?

user2476549

02:38

is there an existing terminal program that can capture and stdout network data? i want to capture all network data over port 23 and pipe it to my parsing program

Faheem Mitha

@user2476549 There's Wireshark. But I don't know if it counts as a terminal program. I'm not sure what a terminal program is.

user2476549

if wireshark offers a guiless option, that would be amazing

cli*

$ tshark -w - does the job, thanks for the direction stranger

Faheem Mitha

@user2476549 You're welcome

Faheem Mitha

03:17

Is it just me, or is this wrong? joelonsoftware.com/about-me

> For my day job, I’m the CEO (and co-founder) of Stack Overflow, a network of Q&A sites visited by 116 million people every month, including 50 million people visiting our flagship site, stackoverflow.com,

I think he means Stack Exchange. But does the CEO really not know what his company is called, or am I missing something?

user2476549

I recall that they changed the name of the company to Stack Overflow (from Stack Exchange) and the network within SO is called SE

We’re Changing Our Name (Back) to Stack Overflow

Jay Hanlon on September 15, 2015

You may know us from such popular websites as Stack Overflow Q&A, Stack Overflow Careers, The Stack Exchange Q&A Network, and most of your Google search results.

Here’s what’s changing:

As of today, our company will be known as Stack Overflow.

Our logo is different. But only a little.

Not one other damn thing.

Here’s what “Stack Overflow” is:

A community where millions of programmers ask questions and share knowledge

The best place to get a job as a developer, or to hire a developer …

but i agree, its confusing

Faheem Mitha

03:35

@user2476549 I see. Thanks for the clarification.

Having read through that post, I still don't understand why they changed the name.

user2476549

03:55

many people felt that by changing StackOverflow to StackExchange they were abandoning their roots as the home for programers and abandoning the community that built them in the first place. obsession with turning SO into a generic q&a site in order to allow easier expansion was turning them into a typical soulless corporate entity that values profits over people, like YA. the name change was largely a symbolic measure to re-assure users that stack will always be developers first

Faheem Mitha

04:16

@user2476549 Hmm. But they're still a network of sites, though. Nothing has changed. As you say, "symbolic".

4 hours later…

terdon

08:25

@FaheemMitha Brand recognition. People know Stack Overflow but don't recognize Stack Exchange.

It's just marketingspeak.

Faheem Mitha

08:37

@terdon Oh, ok.

1 hour later…

Faheem Mitha

10:00

This is a little odd:

root@orwell:/home/faheem# postgres -c "createuser -s taxes"
The program 'postgres' is currently not installed.  You can install it by typing:
apt install postgres-xc

But there is no such package as postgres-xc.

Faheem Mitha

10:51

Relatively interesting thread on politics: politics.stackexchange.com/questions/20711/…

4 hours later…

derobert

15:02

@FaheemMitha yes, the VM was booted off that rootfs

@FaheemMitha I'd suggest using the edit button. Then you can copy & paste from the editor.

Or switch to Perl. Or any other language with sane whitespace semantics.

@FaheemMitha there is.... tcpdump

@user2476549 tcpdump is probably what you want, it can do the capture and output the raw packets to your program. Or of course use libpcap directly.

Faheem Mitha

@derobert Yes, I tried that. For some reason cutting and pasting, at least from a web page, always introduces extraneous white space. Which of course is a problem with Python.

derobert

@FaheemMitha It shouldn't from the edit box. Other than the 4 leading spaces that is part of Markdown formatting, which you'll have to strip. Easy enough to do in vim.

Or presumably that other editor.

terdon

@FaheemMitha copy normally, paste into a clever terminal (terminator and gnome-terminal both support this) and then hold Ctrl down while you select to only get the relevant whitespace.

Alternatively, just paste into a file and remove the first 4 spaces of each line:

sed 's/^    //' file

derobert

15:23

"How does apt-get really work?" great title, makes me so tempted to give some conspiracy-theory answer...

terdon

@derobert Just post a link to Peter Tosh's ♪ ♪ Get apt, stand apt, don't give apt the fapt. ♪ ♪

Faheem Mitha

16:05

@derobert I get 4 more leading spaces every line, I think.

@terdon I usually paste into a file. But I don't think I get a constant 4 spaces every line.

But I could experiment.

They should make a rule that people get rid of that annoying editor_number name after some point.

derobert

@FaheemMitha editor_number name?

terdon

@FaheemMitha You should. Python doesn't like uneven indentation, so it's actually a requirement that you get consistent spacing. The 1st 4 are just the spaces SE markup requires. Remove those and you should have the exact code from the answer.

Faheem Mitha

16:24

@derobert Sorry, that was so garbled as to be completely incomprehensible.

I mean the usernames that start with user. user+some_number.

@terdon Ok. I'll take another look.

To be clear, I'm using X's cut and paste. I don't know what it's called (if it has a name) but it has only one buffer.

derobert

@FaheemMitha What are you pasting it in to?

Faheem Mitha

@derobert Mostly Emacs, I think. But I'll give it another try. Just need to chooose a suitable bit of code.

derobert

emacs in a console?

if it's in a console, it probably doesn't know it's a paste, and is trying to treat it as if you're typing—e.g., doing things like automatically indenting lines

and wrapping

in vim you'd have to :set paste first, but I have no idea what the equivalent for emacs is.

Faheem Mitha

@derobert Oh, Emacs would behave differently in X mode? I guess that makes sense.

@derobert I don't remember. I use Emacs both ways.

terdon

@derobert I don't think it does that. Not by default anyway.

Faheem Mitha

16:33

@derobert What does :set paste do in vim?

terdon

For example, pasting this into an emacs in console mode doesn't make it indent:

while :; do
if [[ -e /tmp/foo ]; then
echo yes
fi
done

And I had opened a file called foo.sh so it was in shell-mode./

It only indented when I hit enter at the very end.

Faheem Mitha

@terdon I've noticed it's not always consistent, though. I think I'll have to try it a few different ways with different pieces of code.

terdon

Which is the same as would happen in X.

derobert

@terdon if you're pasting in a console, the terminal emulator is probably handling the paste... Well, I guess it's possible it isn't. This is middle-click paste?

terdon

Yes

derobert

16:35

@FaheemMitha Turns off all the auto-formatting.

terdon

Same with riggh-click + paste too.

derobert

@terdon Some terminal emulators can be configured to send a start-of-paste escape, then paste, then an end-of-paste escape. Maybe emacs has done that in your terminal. So it could also be terminal-emulator specific.

terdon

Ah, the plot thickens. Fair enough, I have no idea.

Faheem Mitha

AFAIK, apt has never had a custom protocol. Just http(s) and ftp. And I suppose ftp is now mostly dead.

@derobert Suggestions for a tutorial for virt-manager?

derobert

16:54

@FaheemMitha ... you press the "new" button on the top-left???

Faheem Mitha

@derobert Is that it?

derobert

pretty much, that pops up a "wizard" that goes through creating the VM

Faheem Mitha

Do you need to run it as root?

derobert

@FaheemMitha not if you're in the libvirt group

Faheem Mitha

@derobert Ok. And is this significantly different from Virtualbox?

derobert

17:04

Different underlying hypervisor, I believe.

Faheem Mitha

The documentation is quite amazingly sketchy.

@derobert Oh. Is virt-manager more lightweight?

derobert

Donno. Doesn't require any out-of-tree kernel modules though, unlike virtualbox

Faheem Mitha

@derobert I guess that's a good thing.

derobert

And isn't from Oracle. Always a bonus.

Faheem Mitha

@derobert Agreed.

terdon

17:21

@derobert have you ever written any perl programs that execute code over ssh? I have a script that is supposed to ssh to another server (localhost, while testing) run something and then continue. I can ssh fine, the command runs fine, but then it never exits. The weird thing is that this only happens intermittently. So usually it works, sometimes it doesn't.

Does this ring any bells for you?

I tried both using system("ssh $server $command") and using Net:SSH and Net::SSH2. Same issue.

derobert

@terdon I've written things that call ssh... Hmmm... The one thing I can think of is a forwarded session not exiting. I've seen that just running ssh on the console.

Might also be related to connection multiplex (if that's enabled)

terdon

@derobert Yes. That just occurred to me a few minutes ago so I removed the relevant sections from my ~/.ssh/config (ControlPath ~/.ssh/master-%r@%h:%p and ControlMaster auto) but that doesn't seem to have made any difference.

I hate intermittent bugs. . .

derobert

If you can turn on ssh verbose mode (-v), that might help.

ssh -o ControlPath=none should turn it off, BTW

terdon

Would the -v tell me anything I don't know? I mean, I thought that only printed debugging stuff before connecting. I can connect and run my command perfectly well, it just never returns control to the script.

derobert

@terdon it prints debug stuff on connection shutdown too. At least with enough -v's.

terdon

17:29

OK.

Thanks. I'll try that if I can't get this bleedin module to work.

derobert

Though, honestly, I've just sometimes had ssh hang when running from the terminal, interactively. I've always just hit control-C to kill it and never bothered debugging it....

And it happens pretty infrequently.

Faheem Mitha

Can mosh do all the things that ssh can do re forced commands and such?

derobert

@terdon I'd also suggest if you don't need all the forwarding stuff, turn them off. Also can be done with arguments.

terdon

@derobert You mean ControlPath etc?

derobert

@terdon like -a and -x to turn off agent and X11 forwarding. They might be on by default due to the config file

terdon

17:33

Ah! Yes, thanks.

Although what really throws me is that it works most of the time.

derobert

Yeah....

terdon

And seems to be working now. Sigh. Possibly because of the changes in ssh/config.

derobert

@terdon the joy of intermittent problems :-(

It's always fun when "did I fix this bug?" requires statistical analysis :-(

terdon

yeaH:(

Faheem Mitha

18:26

@derobert For virt-manager do you usually go with network install?

derobert

@FaheemMitha I normally use an iso.

Faheem Mitha

Or suppose I fetch a netinst iso, is that useful?

@derobert Would a netinst iso be useful?

Or something bigger?

derobert

I use Debian DVD-1.

Faheem Mitha

Does the network install require special support? Or will it pull everything from scratch?

derobert

Mainly because that makes for a really fast install, even if I want to pull some less-common packages

Faheem Mitha

18:29

@derobert That's big.

I don't have that on hand. How big is it?

derobert

@FaheemMitha DVD-1 is ~4.4GiB

Faheem Mitha

@derobert Yikes. Still, I take your point. It can install directly off the ISO? It doesn't need a real DVD burned, right?

derobert

network install needs to have a netinst image somewhere... I haven't tried that option. But you could grab the Debian netinst CD (~100M) and use that via local media

@FaheemMitha yeah, an ISO. No need to burn it.

Faheem Mitha

@derobert Maybe I'll just install the first DVD of stretch and keep it around.

Otherwise I'll keep redownloading the same stuff.

derobert

best way to get the first DVD is via jigdo, especially since that use your existing /var/cache/apt/archives

Faheem Mitha

18:31

Waste of bandwidth. And I could probably torrent it.

@derobert Oh, right. Good point.

derobert

you could also do CD-1, which is ~700MB

DVD-1 contains all the GUIs if you want them. CD-1 does not.

Faheem Mitha

@derobert DVD 1 would be much more comprehensive, I suppose.

derobert

(Honestly, when I was testing a bunch I grabbed blueray 1.... but that's ~25GB)

Faheem Mitha

@derobert But what about all those security updates? They won't be in DVD 1.

derobert

@FaheemMitha No, but they're much smaller. Most packages don't have updates.

Faheem Mitha

18:32

Or does Debian frequently update the DVDs?

@derobert I thought I saw a ton of those when I was upgrading to stretch from jessie.

derobert

@FaheemMitha Every point release. You can use Jigdo to download the new point release DVDs, using the old DVD (mount it loopback), to avoid downloading most of it

Faheem Mitha

@derobert Point release? For stretch?

derobert

@FaheemMitha Not out yet, but once it comes out, they'll generate new DVDs.

Faheem Mitha

@derobert Oh, right.

Ok, I'll try Jigdo. Thanks.

derobert

Also, if you're going to do a bunch of VMs, set up a web cache, and point apt through it.

Faheem Mitha

18:34

@derobert A web cache for the apt repository?

derobert

@FaheemMitha the installer asks you if you want to use a proxy, you put it there

Faheem Mitha

@derobert ok

derobert

at least if you're using squid, varnish, etc.

Faheem Mitha

@derobert I don't know how to do any of those. I'll probably skip that for the moment.

derobert

yeah, it'll only speed things up for vm #2 anyway. I have squid running at work.

Faheem Mitha

18:38

@derobert I've heard of squid. Is it complicated to set up?

derobert

@FaheemMitha A little bit. Mainly you have to configure the refresh rules. There are also apt repository specific ones, which are surely easier to set up

Faheem Mitha

@derobert I see. I'll shelve that, otherwise I'll never get anything done.

derobert

I'm not sure what the current state of squid-deb-proxy, apt-cacher-ng, or apt-cacher is. Those would be the easy ways. (The first one configures squid for you.)

Faheem Mitha

18:54

@derobert In theory.

There doesn't seem to be a combination bittorrent + jigdo option for Debian DVDs.

Faheem Mitha

19:11

Well, here's an approach - lists.debian.org/debian-cd/2008/09/msg00001.html. But will it work? Who knows.

2 hours later…

derobert

20:53

I guess I'm actually running a slightly patched jigdo...

anthony@Zia:/var/tmp/jigdo$ diff -dbU3 /usr/bin/jigdo-lite jigdo-lite
--- /usr/bin/jigdo-lite 2016-08-10 08:11:43.000000000 -0400
+++ jigdo-lite  2017-06-15 13:33:07.856648269 -0400
@@ -49,7 +49,7 @@
 # Returns 0 (true) if the supplied string is a HTTP/FTP URL, otherwise 1
 isURI() {
   case "$1" in
-    http:*|ftp:*|HTTP:*|FTP:*|file:*|FILE:*) return 0;;
+    http:*|ftp:*|https:*|HTTP:*|FTP:*|HTTPS:*|file:*|FILE:*) return 0;;
     *) return 1;
   esac
 }
@@ -65,7 +65,7 @@
 # Download a file, storing it in the current dir

That adds https support and also runs 4 wgets at a time

2 hours later…

Faheem Mitha

23:22

@derobert Was this your patch? I'm surprised it doesn't already support https.

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