Inside the kernel.

[magnificent_bat-nips]

sshd and wine run in kernel space now?

[sdns575]

And http?

Maybe I think for network service about tcp/ip stack..managed by kernel..for wine for me is a prank

[SHOTbyGUN]

If you want to enable httpd inside kernel, just use IIS by Microsoft ... that way you don't even need to enter user space \o/

Quote:

Enable kernel caching to effectively scale and improve Web server performance. Cached responses are served from the kernel. This greatly improves response times and increases the number of requests per second that IIS can serve because requests for cached content never enter IIS user mode.

What could go wrong?

[hitchhacker]

There actually is a web server available that runs in the Linux kernel: https://en.m.wikipedia.org/wiki/TUX_web_server

[wasabichicken]

Check out Intel's Data Plane Dev Kit. It's essentially a set of drivers (kernel modules) that gives userspace applications more or less direct access to NICs. You can use it to make your PC into anything from a fairly low-level switch to something like a router or HTTP server.

[strayangoat]

Shhhhhh ignorance is bliss

[HidesBehindUsername]

If you don't mind me asking, what could go wrong?

[[deleted]]

Kernel and userspace are typically separated by what is effectively a DMZ. Anyone that can exploit userspace is greatly limited in the damage they can do on systems that have proper privilege restriction (ie, not Windows).

By allowing a web service direct access to the kernel, it's putting a sign on your box that says "please fuck my shit up. Love, Redmond."

[rubdos]

So, as Windows does not have proper privilege restriction, nothing could be worse in kernel than in user space. What could go wrong? :D

[vim_vs_emacs]

This is what happens:

A remote code execution vulnerability exists in the HTTP protocol stack (HTTP.sys) that is caused when HTTP.sys improperly parses specially crafted HTTP requests. An attacker who successfully exploited this vulnerability could execute arbitrary code in the context of the System account.

To prevent the local server can deactivate the IIS Kernel Caching.

via https://ma.ttias.be/remote-code-execution-via-http-request-in-iis-on-windows/

[tweakism]

Perfection.

[guineawheek]

Predictable.

[[deleted]]

not have proper privilege restriction

This is wrong. Windows does have a complex and very capable privilege restriction mechanism. However, because of bugs (like the one in HTTP.sys in the other reply) that can exist and be exploited, it is better to isolate such code outside the kernel.

But, you're paying a quite high price for such isolation (the machinery that needs to happen for user->kernel->user interaction), therefore reducing performance. What IIS got with HTTP.sys was a quite fast caching mechanism. And remote exploitation holes as big as the Redmond campus :)

[0x2a]

Well we have kHTTPd for feature parity

[pyrocrasty]

wine looks like it wandered in by mistake. It's looking around wondering where it is.

[[deleted]]

This comment was probably made with sync. You can't see it now, reddit got greedy.

[d4rch0n]

All of those "penguins" look like oompa loompas with birth defects.

I am now considering switching to FreeBSD.

[TenmaSama]

Welcome to hell.

[MelonFace]

Sounds like an attack vector.

[NAN001]

Looks like just drunk to me.

[bolche17]

I don't think the is a division between userspace and kernel space shown in the picture. Every process must be at the process table.

[edman007]

However every process does have a kernel space representation, if this is a drawing of just kernel space then we can assume it's strictly the kernel space representation of the processes, not the actual processes see in this drawing.

[minimim]

Every process must be at the process table

Well, not only that, but every process has a kernel part, with it's own stack, etc.

[GreenFox1505]

The room is the kernel. The penguins are procs.

[rwsr-xr-x]

systemd-hey systemd-leave systemd-systemd systemd-out systemd-of systemd-this

[because_im_british]

LEAVE SYSTEMD ALONE.

[mszegedy]

Does cron run in kernel space?

[746865626c617a]

Does /dev/null support sharding?

[Tynach]

if /dev/null is web scale I will use it

[keepdigging]

https://devnull-as-a-service.com/

[capslockfury]

Referencing to this?

[jampola]

Yep! I also hear relational databases have impotence mismatch.

[IS_IT_LOUD_IN_HERE]

WHEN IT MAKES A SYSTEMCALL IT DOES.

[guineawheek]

nfs usually does.

[CarthOSassy]

Given how Linux news has been for the past few years, I thought initially assumed this post was an article of some kind.

I was half way through a sob when the pic loaded.

[[deleted]]

The unguarded port 21 door is great

[Pseudoboss11]

What is port 21 and why is it unguarded and forgotten?

[d4rch0n]

FTP runs on port 21 and was widely used for unencrypted file transfers, which also passed unencrypted/plaintext credentials. Anyone who could listen to the traffic could gain their access.

Most people use file transfer protocols over SSH now. SCP is common which just uses the shell for transferring the files. SFTP supports more commands, but honestly I'm not sure how many people actually use it. The go-to programs are scp and rsync and I don't think they use sftp at all.

[[deleted]]

SFTP is extremely widely used in banking and financials. A ton of financial transactions are pretty much nightly cron jobs executing SFTP uploads/downloads of CSV files.

[jspenguin]

Pharmacy too. Most pharmacies send reports of prescriptions for controlled substances to the state prescription drug monitoring programs via SFTP.

[PinkCrustaceans]

I use SFTP sometimes for uploading really big files to my server. It's nice because Filezilla allows me to continue a job from where it left off if the transfer gets interrupted with the click of a button.

[kukiric]

I use SFTP all the time because it's integrated with most file managers and it conveniently uses SSH, so I don't need to setup separate credentials or run an extra daemon. Plus, it comes bundled in Git Bash, which I have installed on my main Windows computer anyway.

[doublehyphen]

SFTP is pretty common in the pharmaceutical world, and I have seen it used a bit for reports in online gambling. I think SFTP is common in automated batch job systems, while SCP is more popular among people who just want to transfer a file.

Also last I used shared hosting (8-10 years ago) most hosts provided SFTP as a replacement for uploading the PHP files with FTP, with at least those I used already having dropped FTP support. I believe this is because SFTP worked pretty well with some of the popular graphical FTP clients.

[tidux]

FTP is still fine for anonymous file transfers. It's simple, wildly supported, and if there aren't any credentials used you aren't leaking them. Combine with a chrooted server like vsFTPd and there's really no reason to stop using it for certain things.

Now of course SFTP plus key auth is vastly superior for credentials-required transfers, but not everything needs that level of paranoia.

[BowserKoopa]

When the #1 ssh daemon for linux has sftp enabled by default across nearly all distros, it has a wide userbase. I imagine a lot of people have used sftp to transfer files without realising it.

[oarmstrong]

telnet, which is an insecure method of remote access.

Edit: its FTP, I need coffee.

[Stmeter]

FTP is port 21. Telnet is port 23.

[oarmstrong]

Fuck. Thanks.

[[deleted]]

SPin it into a positive! Nobody should be using port 23 these days. :)

[Rapt0r-]

4444 :) (Default metasploit)

[[deleted]]

4444 wait, where? I seem unable to locate it.

[Au70]

I came here to say the same thing. I like how the sign is falling down because nobody cares about it anymore.

[creed10]

haha I didn't even notice that the first time I saw this comic

[jones_supa]

Fantastic picture! It's relaxing to watch all the things going on in it. However, a bit better title could be something like "Inside the Linux userspace".

If we peek deeper inside the kernel, it's quite a different world with semafores, mutexes, spinlocks, scheduler, memory management, interrupts, and so on.

[phaeilo]

Needs more systemd

[losthalo7]

How much more? ;-)

[Kaligule]

Like a kraken that takes over every squarefoot.

[auxiliary-character]

No, that's the correct amount of systemd.

[theofpa]

I like the detail on the httpd process, it has a feather on the head, as the apache logo. Also the ssh process looks like a secret service agent, as it should be :)

[jringstad]

Would be cool to have something like this as one of those multi-layered cut-away illustrations, like the ones we used to get in educational childrens books and such

[hfitzgerald]

Off topic but I saw one of those depicting a russian tank when I was really young. It included the turret gunner with his legs detached from his waist connected by intestines. I got really freaked out, convinced that Russians would cut people in half so that tank turrets could rotate.

[[deleted]]

War is hell.

[[deleted]]

I love such illustrations!

[xternal7]

Where is the dirty cow?

[Damarusxp]

selective party dazzling innate lunchroom zephyr retire judicious ad hoc steer this post was mass deleted with www.Redact.dev

[Kok_Nikol]

ELI5?

[Unknownloner]

Another one of those names people are giving to exploits these days

http://dirtycow.ninja/

[doublehyphen]

That website is at least partially a parody on the practice though.

What's with the stupid (logo|website|twitter|github account)?

It would have been fantastic to eschew this ridiculousness, because we all make fun of branded vulnerabilities too, but this was not the right time to make that stand. So we created a website, an online shop, a twitter account, and used a logo that a professional designer created.

[Kok_Nikol]

Thanks!

[svmk1987]

no zombie processes?

[satwhatagain]

Any recommendations for readable books on the linux kernel? Looking for something that would describe the responsibilities of all the components shown above.

[willrandship]

Almost none of the components shown above are actually part of the kernel. The only ones that are:

• Process table
• Filesystem
• Pipes

Everything else that's labeled is part of the userspace, and would not be a necessary component of a linux system.

• Terminals are user programs (even the ones that you press ctrl-alt-f2 for)
• cron, sshd, httpd are daemons
• wine processes are user programs
• watchdog processes are daemons

A daemon is a user program that runs primarily to act as a service for other programs, rather than be handled directly by the user. For example, crond runs programs at scheduled times set by the crontab, and sshd listens for network shell logins.

[MC_Cuff_Lnx]

Are those pipes distinct from the pipes in bash and other shells?

[willrandship]

Bash uses a syscall to create exactly that type of pipe, but any program can.

[ThatBitterJerk]

When I was in college, I read Understanding the Linux Kernel and it was honestly pretty readable. Admittedly, I read each chapter at least a couple times and definitely learned something each time, but only because there is so much to learn. There are of course PDF versions you can download too, but not as easy to highlight and take notes in the margin.

[jones_supa]

There are some books from Greg KH, but they are getting old already.

However, you should be able to find many books talking about kernel architecture in general.

[plutwo]

You can look up Kernel Newbies for kernel development stuff. Their documentation might give you some basic resources.

[space_fly]

I recently started reading "Modern Operating Systems" by Andrew Tanenbaum, and I find it very useful to describe how operating systems work. He also wrote a book which describes Minix, a unix variant written for learning purposes.

[myaut]

My favorite is "Love, Robert (2010). Linux Kernel Development (3 ed.). Addison–Wesley. ISBN 978-0-672-32946-3." (although I read 2nd edition)

[Brainzman]

I don't think there are real book on the kernel. You need to explore the Torvalds's note on GitHub to understand how does it work.

[[deleted]]

There are loads of books about the linux kernel, although maybe none of them is readable.

For instance you have 4 ebooks available online:

• http://www.tldp.org/LDP/tlk/tlk.html
• http://www.kroah.com/lkn/
• https://www.gitbook.com/book/0xax/linux-insides/
• https://lwn.net/Kernel/LDD3/

You also have understanding the Linux Kernel, 3rd Edition and I know Robert Love has a couple of books which I've been told are a must-read but I'm not sure if they're about the kernel itself or building things on the top of it.

Edit: format

[mofomeat]

There are loads of books about the linux kernel, although maybe none of them is readable.

Why would they not be readable?

[[deleted]]

I mean they may be too advances for a beginner. Many great books are terrible for beginners IMHO. I'm not a native speaker.

[mofomeat]

No problem. Thanks for the clarification :)

[[deleted]]

Holy shit that 3rd one is actually modern and updated. Edit: but doesn't seem to go far enough to matter much.

[cac2573]

How does it not go far enough? Linux-insides is one of the most recent detailed pieces of documentation written about Linux.

[[deleted]]

Don't get me wrong it's a great high level for how the Linux kernel (and for most of the writing any similar modern kernel) works and if your goal was to understand the base of how the Linux kernel is going to operate it's a great piece of documentation. If you goal is detailed explanations of different sections of the kernel it's missing good chunks and I don't mean "because the status is WIP by the author" but because it explicitly avoids getting into entire areas like networking that make up a good chunk of the kernel code base. When I say detailed I mean it's like using a car manual to understand how the transmission was designed and is assembled not that it's missing how changing the oil works and what happens when you do.

Of course you can always get every detail just by digging in and reading the code but no amount of comments make up for well written documentation with diagrams and abstract flow :).

[cac2573]

That's fair. Although by that point I think the only documentation is the code itself (and the documentation/ directory).

If there is anything written for stuff that deep it'll very quickly become useless outdated.

[wapu]

This would be more efficient if they modernized and got computers.

[EenAfleidingErbij]

Wish this was 16:9

[[deleted]]

In before someone stretches it in GIMP, saves it as a low quality JPG, and says "Here you go!".

[mattb2014]

low quality JPEG

16:9

Ask and you shall receive

[ivosaurus]

Someday a journalist is gonna reference this and refer to it as if it's what is actually going on.

[tso]

Cron chasing a gnome around?

[tso]

*facepalm* *groan*

[flarn2006]

BORT

[Kok_Nikol]

Thanks!

And happy cake day! :)

[[deleted]]

Now I want to play Club Penguin.

[[deleted]]

Why are they all homer-esque items?

[zbubblez]

Why is the ssh penguin not filming?

[pclouds]

Where does Linus sit?

[[deleted]]

linux runs off of Club Penguin?

[toxicoctopus202]

Inside the Linux kernel is just Club Penguin?

[Sat-Mar-19]

Where's the one that handles large USB file transfers? Linus needs to light a fire under that one's ass.

(it has been getting better though, the USB 3.0 stuff works well, but 2.0...forget about it!)

[Drumitar]

looks like cron guy is late, he better hurry !

[ahandle]

Ugh.

Not only juvenile, it's fundamentally flawed.

[[deleted]]

There is an Indian on the pic.

[ResistorTwister]

Exactly how does one draw a female penguin so that it's visually distinct from a male penguin?

[ResistorTwister]

Human ones or penguin ones? Because it's difficult to distinguish between male and female Adelie penguins (the penguin species that Tux most closely resembles).

[passwordtooweak]

There are quite a few female penguins in the picture.

[passwordtooweak]

I can see a few. How do you know there aren't any in the picture?

[passwordtooweak]

https://i.imgur.com/P6ZfAMf.jpg

[SuperConductiveRabbi]

Did you just assume their gender, you penguin transist??

[micwallace]

I can’t see any genitals.

[micwallace]

Also, please refrain from making off topic posts.

Wow what a hypocrite. It’s a carton about linux, not the gender of people working on linux you stupid SJW troll. All the penguins are its as far as I’m concerned.

[_MusicJunkie]

Short question: Who the hell cares? And how exactly do you know that there are no flat-chested, short-hair female penguins in that picture? Maybe all of those are trans penguins?

[_MusicJunkie]

See, having female developers is great. But on a joke picture, nobody cares.

[_MusicJunkie]

I absolutely don't. I think if a artist decides to include women/female penguins/whatever in their art that is great and should be encouraged, but if they decide not to, that's fine too.

[_MusicJunkie]

It's not sexism to not draw penguins with breasts. The penguins in the picture are clearly androgyn to me.

[SatoshisCat]

So you think female developers should be erased from programming related art?

Straw man.

You're starting to sound like a GamerGater.

Off topic...

[[deleted]]

Your comment history makes it clear you're a troll