@sindhu

They will ask how to replace foo with bar in a text file and get a nice informative answer explaining how to use sed and the substitution operator to run s/foo/bar/. They then turn around and post another question asking how to replace bar with baz without any attempt to use the knowledge they gained in the previous question.

They will refuse to give the information required in order for us to understand and help them and will then be abusive and rude towards the people who try to explain that they can't help without it.

They will refuse to ask questions on the main site and, instead, will ping random users in chat, bugging them for help.

They won't spend the 5 seconds on google that would have given them the answer. You take the title of their question, paste it into a search engine and the first 10 links provide the answer.

I've even seen people post photographs of their homework assignments. They don't even take the time to write it down as a question.

@terdon s/time/will/

oh wait

@terdon meta.unix.stackexchange.com/q/3723/66803

So, if I connect to a remote machine using VPN, do I need to use ssh to actually connect to it?

I don't know how VPN works - I've never used it.

Also @FaheemMitha what do you think about?:

@Pandya You forgot the actual question.

which?

Oh, I see. The title is the question.

I'd move it into the actual question, personally.

on-topic and scope aren't exactly the same things, are they?

Oh, SO thinks they are. Well, fair enough, I guess.

Ok, upvoted.

I'm not sure, actually. Do we maybe want on-topic, off-topic and scope? Or does that not make sense and we may as well have everything under scope?

Yes, on-topic and off-topic can be under the scope.

Yeah, I guess there's not much point in having them separate.

See meta.unix.stackexchange.com/review/suggested-edits/54

@Pandya fair enough. Synonym added

@terdon thanks

BTW, can I have a status-completed for meta.unix.stackexchange.com/q/3723/66803 ?

done

ok

:) why you not use "Terdon" instead of "terdon"?

Because it's also my username and I'm used to seeing it in lower case.

ok. good-bye

"Does anyone know of a method to discover all of the files read by a given Linux process tree?" Just asked on #clasp on Freenode. I'm thinking strace, but is there anything better?

@FaheemMitha Can't lsof do something along those lines? I don't know how, but it sounds like its kind of thing.

@terdon lsof lists open files.

Hmm, one can apparently restrict per process. But I've never tried it.

@FaheemMitha Yes, by a specific process. Isn't that what you want?

@terdon Possibly.

@FaheemMitha You might do it with auditctl, possibly

@JennyD Ok. Does that require any special setup?

@FaheemMitha Just turning auditing on, which you do with auditctl. Its man page is fairly extensive. The downside is that it does slow the machine down a bit.

@JennyD ok

@JennyD Do you have experience using the audit system?

@FaheemMitha A little. I've set it up on a CA server, but that's a while ago. I've not used it on any server that had any kind of heavy load.

@JennyD isn't that precisely what lsof is for? It's one of those commands I know of but have very rarely used. I only ever use it to see what's blocking my umount command, basically.

@JennyD Can audit give detailed info like when a file is read or written to? On a per file basis? Any handy tutorials?

@FaheemMitha Yes. Here are two examples:

@terdon lsof tells you what is happening at a given time. But it isn't designed to be used for tracking.

@FaheemMitha And continuous tracking is exactly what auditd does best.

I don't have a link to a tutorial, I found what I needed based on the man page

@JennyD Yes, I see.

@FaheemMitha Oh, you mean after the process has finished?

By the way, why aren't you posting this as a question? It sounds like a useful one to have.

@terdon No, I meant as time goes on. Suppose you want to know what files are being closed and open as a function of time?

In other words, follow your own advice :P

@terdon Well, this is probably bog-standard functionality.

I don't want to look like an idiot.

If there is a specific use case there are problems with, then sure, I'd post.

@FaheemMitha I'm sure you won't. And hardly bog standard. If neither you, nor I, nor Jenny who knows a hell of a lot more sysadmin stuff than we do can answer in a couple of words, it's not going to be quite as simple as that.

@terdon Ok.

@JennyD What do you think? What kind of question would be suitable?

@FaheemMitha I'd be happy to help you figure out a suitable rule set, but I agree that it'd be better to do it as a question. I'd start by figuring out what exactly it is you want to keep track of - is it "what programs are touching this file", or "what files are being touched by this program"

Plus, I can see Stéphane, cuonglm and Gilles lurking so you've already outed your ignorance to all of the top 5 rep users except slm :)

lol

Also derobert. Who's actually quite likely to know the answer.

@JennyD Well, I'm having a simultaneous conversation on #clasp on Freenode.

I think the issue is getting rid of useless files in a codebase.

(Which might actually be a better question to answer.)

One way of doing this would be to check which files are actually used in a build.

You could always do something like strace command 2>&1 | grep open

Someone there suggested atime. I've not used that. That's time the file was last touched, right?

@terdon True, but strace is quite chatty. Plus dupes/false positives.

@FaheemMitha nod It might also be a on-topic on SO, there might be some tools for whatever language is being used in the code base to figure stuff like that out.

@FaheemMitha Hence the grep open.

@terdon Well, a file could be opened many times.

@JennyD True.

May be with use of /dev ?

@MostafaShahverdy I don't understand the question. Do you want to extract text from a PDF file?

@FaheemMitha my final goal is to encrypt a pdf file without saving a copy of it in disk.

@MostafaShahverdy Oh. Then you should probably pipe it directly.

Yeah, how can I pipe it from withing some kind of application like abiword?

@MostafaShahverdy You'll need to give more details. Is your content sensitive? A word processor will automatically be writing to disk, I think.

yes my contents are sensitive. for abiword iit won't be an issue.

So far we used to write some data withing abiword, convert it to pdf, enc the pdf file, and then send the encrypted file through email, etc.

within***

there is a gap here that each time the writer had to "permenantly delete the un-encrypted pdf" manually (and usually they forget to do so. they simply put it in trash by mistake)

@MostafaShahverdy You could always save the PDF in /foo and have a cron job that deletes any file in /foo that is older than 5 minutes or so. Have the cron run every minute. Would that do?

@terdon the first thing that came to my mind was a way to send the content directly to a device in /dev and somehow work with pipes.

Do the abiword conversion programatically, along with the encryption.

Then just include the deletion of the file in that script.

@MostafaShahverdy I don't know if that's possible. I don't know how the print to pdf feature works. Would it just send the raw data to the /dev/tty or would it overwrite it and destroy the tty?

I assume you are trying to avoid actually writing the data to a file at any point, right?

This really should be asked as a question on the main site. Sounds interesting.

abiword --to=pdf filename converts to PDF.

@terdon write. Exactly.

@terdon Clearly he isn't. Since Abiword would certainly write to file.

@FaheemMitha Yeah, but that requires the file to have been created first. I think that's what Mostafa is trying to avoid.

@terdon If you write anything in a word processor, you're writing to a file somewhere.

@FaheemMitha No, not if you don't save it. It might write to a tmp file internally or it might keep everything in memory, I'm not sure. Either way, it won't be a normal file.doc kept in the user's $HOME.

It's not like it's floating in outer space. I suppose abiword gets rid of temporary files when it exits, but you do have to exit it.

@FaheemMitha that's right.

@FaheemMitha Are you sure it will be writing to disk and not a tmpfs or just memory?

@terdon True, it won't be kept in $HOME. But does that make a difference?

@terdon No, I'm not sure about Abiword. But generally word processors and editors write to file, because they don't know how much memory is available.

I think.

@FaheemMitha Not much, but it's a step in the right direction. I'm still not sure if any actual files are created on the HDD. Presumably, Mostafa wants to avoid the possibility of data recovery software being able to find it. If the tmp file was never saved to disk but only in memory or tmpfs, that shouldn't be a problem, right?

Unless you explicitly direct them otherwise. But I don't know if RAM is possible. And is writing to RAM necessarily more secure?

Actually I want to avoid files as far as possible

@FaheemMitha It should be, yes.

@MostafaShahverdy Faheem's point is that no matter what you do Abiword will be writing to a file somewhere. If that somewhere is in memory, you should be OK, if it's on the disk, the whole operation is pointless.

It all depends on the level of security you need.

@terdon I we can configure it to not to.

@MostafaShahverdy Oh? How?

Generally sticking stuff in RAM without asking the user is kind of bad manners. I don't think editors/word processors generally do that. Because often RAM is limited.

Where will it keep the data you have written then?

as far as you keep the text not that long it won't be written on disk. Abiword uses chunks of ram

as far as you occupy one chunk (of its size that I don't know) everything will be kept in memory

@MostafaShahverdy OK, are you sure? I can confirm that I don't see anything obvious created in /tmp or /proc/ABI_PID.

@MostafaShahverdy How long is "not that long"?

Well, strace should say...

I'm not sure

I just know that there is a chunk thing there

and it has a limit

Ok.

if you don't pass that limit nothing will be saved on disk

Odd. Emacs saves everything to disk by default.

I think Vim does too.

well

using vim everything is different!

currently I can do the same job using vim

I have even written a plugin for that for vim

but my boss didn't accept it, because its only text, while our users needs to send diagrams as well

That would actually make an interesting question. Where do editors/word processors write temp files?

and of course most of them don't know how to exit vim :D

@MostafaShahverdy You can make diagrams using text. E.g. PGF/TikZ. And similar programs.

@FaheemMitha I doubt his boss will accept sending all users on a 2-week LaTeX/TiKZ course as a viable solution ;)

@terdon 2 weeks? I wish.

True.

also I looked forward a way to pipe the output of the content itself, and not printable pdf versoin

Actually, if you type stuff into an emacs scratch buffer, it's not clear where it is being written.

@MostafaShahverdy Ask a question on the main site, someone might have a clever idea.

@FaheemMitha Memory, presumably.

@terdon Possibly.

It might be possible by creating a named pipe attached to the encryption process and telling abiword to write to that.

@terdon Its very difficult for me to describe what I want there :D

@MostafaShahverdy You did a pretty good job here. Just do your best and we can help clarify it.

@terdon give me a few more minutes here, then I will ask it there

@terdon can you explain more?

@terdon if I was able to tell abiword to write to stdout I would be able to do anything

@MostafaShahverdy Not really, it's just an idea. I don't know if it would even work. I thought that maybe you could create the named pipe and use the print to file thing to write to it.

Hmm. I just tried and it doesn't seem to work. Might be doing it wrong though. I really don't know much about named pipes.

can't you use an encrypted file system for temporary storage? cryptfs or whatever it's called?

or get an encrypted USB stick like Ironkey, that will lock itself when not in use

I can use it for myself. but how about other users?

they are not able to deal with it

the ironkey is quite easy to use, but it's not inexpensive

I had cryptmount in my mind for that...

the thing is, with security, the weak point is always people, not technology

and you can have either high security, or high ease of use, but rarely both

So, VPN. Has anyone here used it?

@FaheemMitha Which one? OpenVPN? Any VPN?

@Fabby AnyVPN.

Good night! I'm off. Ping me about thsi tomorrow!

I thought you were going to sleep.

Yes I did...

@Fabby Ok.

@FaheemMitha So, what do you want to know about VPNs?

(I was going to, but I'm willing to entertain you a few minutes more)

@Fabby Oh, don't worry about it. Go to sleep. It's not urgent.

Well, I'm going to have a smoke first. I've left all other rooms, so... Fire away @FaheemMitha

and the expression was; give someone a fish and he'll not be hungry for a day.

@Fabby Well, suppose I want to log into a very remote computer.

Teach someone to fish and he will not be hungry for the rest of his life...

And that computer is only accessible via VPN.

Write evrything down,; I'll have a smoke and respond when I get back.

Do I used both VPN and ssh to connect to it?

I've never used VPN.

First VPN, then ssh?

Also, smoking is bad for you.

It depends how the computer was set up: you might just have to connect to the VPN or you might have to use ssh and VPN

A VPN is just like a tunnel:

TCP/IP over the Internet is the mountain

and VPN is the tunnel through the mountain.

So just a VPN might suffice? And it might give me a shell?

no...

VPN'll just give you network connectivity

how you use the server depends on the server:

might be ssh, web access, application access... anything, really.

VPN is like a really long Ethernet cable.

@Fabby So you'd need to ssh then.

that's al it does.

I dunno: if it's a Windows server, I'd be surprised it had ssh.

you might have to use RPC...

Like I said: VPN is just network connectivity: what's on the other hand depends and I can't answer that for you...

:-(

Sorry... A bit like the apples, really.

(this answer)

That's fine. It sounds like I'd have to get the VPN thing running, then ssh. But I'd have to actually try it...

If it's a *nix server on the other side: yes.

Good enough?

I can go to sleep now?

@Fabby Yes, thank you.

You're welcome!

@Fabby Have a good night. Take care.

(you owe me one!) :P

Good night!

@Fabby One what? One apple?

@FaheemMitha you still want to use ssh over a VPN, mostly because you don't want to run an open telnetd.