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Introduction to User-Mode Linux
developerWorks writes "Ever wish you had a place to let your Linux applications play -- where they wouldn't hurt anything else? Do your killer apps spend too much time killing each other? Originally conceived as a kernel developer's tool, UML lets you set up multiple virtual machines that are isolated from each other and from the hardware. Now, you can test applications all the way to failure without breaking the host system -- or even requiring a reboot. Veteran administrator Carla Schroder shows you how in this tutorial."
How can a tutorial that requires registration get accepted?
The link requires (free)registration. It has a guide for Debian installation too. For Gentoo users, you may also look at gentoo's guide on User-Mode Linux.
A couple of years ago, I went on vacation with no net access and only my laptop. I wanted to do network programming during my vacation. I set up four VMWare virtual machines running FreeBSD and did my little program (user-mode NFS server). Got a lot done in a short time (probably due to the lack of net access - had all the necessary docs saved ahead of time). I chose FreeBSD because it was much easier to cut down to a tiny image than any Linux distro (even Slackware, my favorite).
VMWare is also useful if you want to do OS-level programming (eg, write a kernel). This is one of my spare time projects (haven't touched it in years, though). I'd imagine user-mode Linux can't let you mess with the low-level stuff, but it could be useful for high-level stuff like scheduling algorithms and so forth (useful because it's a real PITA to boot up a machine whenever you change a line of code and user-mode Linux might give you some better debugging options than a serial cable).
You might be able to do this with Bochs nowadays, but Bochs was nowhere near useful back then. Seems to have come a long way in a short time.
Not sure what advantages user-mode Linux would have over VMWare or Bochs. Perhaps some karma whore would like to register and post the contents of the article :)?
What would really be interesting is if non intel hardware could also be emulated. I sure wouldnt mind an Ultra5, RS/6000 and hammer systems networked together with ipv6 on token ring.. all on my BeOS desktop. BeOS is supported isnt it?
"Give orange me give eat orange me eat orange give me eat orange give me you." -Nim Chimpsky
UML.. User Mode Linux or Unified Modeling Language?
BSD.. Berkley Source Distrobution or Blue Screen of Death
sheesh
all we need now is Xylophone Medical Laproscopy, Super Qualatative Logon, and our hype acronym heaven will be complete! "MWAHAHAHAHAHAHA"
I cant substantiate, I've tried searching, but I remeber reading (back when /. annonced it was going to a subscription model) that once per day they would post a advertisement/story. I think it was Rob who posted it. None-the-less, That was the deal that kept the bits flowing.
...could this be a possible way to have "more" security while running and hooked to the net? Is there any angle here to make the virtual OS that's connected be totally locked away from the actual OS that runs everything, so that in the event of a major "owning" you could delete that virtual system, then reproduce it easily from a "spare" OS with it's set of apps that's already installed and clean? Sort of like the knoppix idea?
Still, there were features that would make it ideal for such a situation. When the console boots, you can redirect the console output to a serial line or to a TCP port, so the system starts, then halts until you connect to the TCP port to monitor the progress, then it continues and you see the console output in a terminal window as if you were sitting at the console.
Before someone starts modeling OOP with this tool, they should get a new acronym. Why is it so hard to think of something original?
Now, you can test applications all the way to failure without breaking the host system
isnt that the point of a protected mode operating system?
Why stick up for big business?
--the only thing I've done along these lines is to have a "spare" old hard drive with a basic system installed, that isn't plugged in to anything, but it's mounted in the drive bay. If I get a bad fubar, I'll more or less know what the last thing that happened was, so with the spare drive installed I can avoid that problem whatever it was before going online. But ya, it would sucketh to lose all the data and updates. I don't trust my level of expertise to make a backup dump or raid system all that valuable, as more or less I am as likely to just "backup" the virus or trojan should it become installed. I'm just a casual home user, not having to defend expensive server farms, etc, so the requirements aren't as great, but it still would be nice to have an easier to use method that what's available now, which is to become a security guru in your spare time. A virtual system that ran completely in a jail would be a good idea. I tried knoppix but it has some features I don't like (primarily I'm a gnome not a kde guy) and I couldn't make it dial out), but still, it's a step in the right direction and it ran surprisingly fast, much faster than I thought it would.
To get back to the subject, YES, an additional layer of "permissions" to access the system. Two stage isn't enough, you should be able to do an instant "create on demand" full system, use it for a session then trash it, thereby eliminating anything nasty that might have occurred to you, and that temporary system could be an additional step-->out away from the actual root or user level. There should be a "this is vulnerable being online so it can't do much and nothing permanent without jumping through hoops" temp-user level. A temporary trip wire action would help, and then the system would force you to go offline and compare audits before anything was 'saved' to the disk in either a users directory or at root level. It would be saved in the virtual OSs ram cache or on swap (a "virtual swap" inside the real swap as well?), examined, if it passes, THEN it can slide downhill into normal user-space. And the box needs it's own built in battery to keep ram cache intact in case of catstrophic outside failure, so that very important but still unexamined data is not lost. I've had UPSs fail, but when a laptop was plugged in, it didn't matter, I didn't lose anything or suffer file system damage, the built in battery concept is ideal for this, and I have no idea why it isn't just common on desktops as well. They are already big and heavy, a small battery is not that much more weight or space.