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Old 01-24-2002, 11:23 PM   #1
okok
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Question UMSDOS vs. loop device


Hi, I am considering installing either winlinux 2001 or phat linux on my windows pc.

Winlinux uses UMSDOS, and Phat linux uses "Ext2 Linux file system "by mounting it on a loop device" (not that I understand what this is...).

I would be glad if someone could explain me what each of these systems are, their advantages and their disadvantages.

Also, I am interested to know whether the entire directory tree and files that exist on a shared drive can be seen and accessed by both systems.

Thank you
 
Old 01-25-2002, 12:13 PM   #2
Thymox
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Ok. You really should go for the Ext2 in a loop file.

UMSDOS: It directly accesses the Dos file system and uses that for it's file storage. It has some weird addon thing (that only Linux can see) to manage the ownership of files. If I remember rightly, it used to be used quite a lot. Bit dodgy if you ask me.

Loop file. Basically, in order to understand this, you should understand how Linux handles filesystems. Windows used to use Fat16, and now used Fat32. NT uses NTFS. These are all filesystems and have their own advantages/disadvantages. Ext2 is the default Linux filesystem. Unlike dos/windows where each partition/device has it's own 'drive letter', Linux can 'mount' the devices whereever you want it to. CDs use ISO9660. Ok, you've got the filesystem bit so far.

Since all things are considered as files under Linux (there's a how-to for this, somewhere. Look at the ldp site), you can therefore 'mount' a file as a complete filesystem. This way, you do not need to repartition your harddisk, but you also do not risk everything on your current Windows partition.

In short, (what are you cheering for?) using the loop filesystem will create a couple of huge files on your existing Windows partition, and Linux will reside within these files.

If you want to try Linux, without the hassle of repartitioning, then go for the loop filesystem one. It is also a little safer. Should you decide (God forbid) that you really don't want to do Linux anymore, you just boot into Windows and remove the files.

Any more questions, just post.
 
Old 01-25-2002, 12:44 PM   #3
okok
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more UMSDOS vs Loop file system questions

Thank you, this was a good explanation! Two more questions:

First, in what way is the loop filesystem safer than UMSDOS? What risks are involved in useing UMSDOS?

Second, I already heard that winlinux (which uses UMSDOS) can access dos/windows files. Do you knwo whether a linux running from a loop filesystem would is able to access files created under windows/dos?

Thanks
 
Old 01-28-2002, 12:04 PM   #4
Thymox
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Using UMSDOS you have the opportunity of editing your Windows config files, mistaking them for the Linux ones, so when you boot back into Windows, everything has gone cock-a-hoot.

Loop based filesystems act in almost exactly the same way as a proper partitioned system, except that it is slower. If you want to edit your Windows files, then you must mount the Windows partition (even though it's residing on it anyway) to do so. With UMSDOS, because the files sit side-by-side, you can access the Windows files with no hassle.

The UMSDOS system was a good idea before computers were powerful enough to cope with loop filesystems, but since they are now, I would go for the loop one.

The only real disadvantage that you will see using the loop based one over a proper partition based install is that of speed. Because the complete file-structure resides within a file, it is not exactly fast.

Here's an example of where loop systems are also used. On the cover CD/DVDs of computer magazines, you might find .ISO files ready to be burned to CD. Under Linux, you do not need to burn these files to CD in order to access the contents. You can mount them as a loop filesystem.
 
Old 01-28-2002, 01:53 PM   #5
okok
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Thank you Thymox

Your explanations are excellenet.

I wonder why it is so difficult to find clear explanaitons that people almost without technical backgrond like myselft can understand...
 
Old 01-29-2002, 12:12 PM   #6
Thymox
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Don't worry about it. I've been using Linux for about 18 months now, so I still consider myself a newbie. The biggest differences I have found between Linux and Windows is the whole concept thing. As far as I am aware, Windows was built ontop of a system that was designed to be used on a standalone machine. Linux comes from a long line of unix like os's, which were designed to work as a network of machines. Because of this main difference, there are many conceptual differences. Take the mounting thing (which I am still trying to explain to my housemate, who now has to use Linux because of his Uni course), for example. Big conceptual differences between Windows and Linux. Still, it never does anyone any harm to learn new things!

As for the explanations thing... I think you'll find it's almost a foregone conclusion. The more you learn about Linux, the more technical your explanations can become, and therefore when dealing with situations that you consider to be simple, you almost gloss over the subject - expecting the other user to instictively know what you're talking about. Being only a recent convert to Linux, I understand how frustrating this can be for newbs, so if needs be, I try to keep it as untechnical as possible.

Thanks for the compliment - I could do with them at the mo, bloody university dissertations!
 
  


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