Linux question - mount fs in Windows?

[Jimdoria]

Hi everyone (especially the Linux gurus out there...)

I'm a rank noob when it comes to Linux, but I've been experimenting with QEMU-Puppy on a USB stick, and so far I like it very much.

Puppy Linux runs from RAM, and when you are done and shut it down, it saves it's changes back into a file system on the media from which it was run (thumb drive in my case.) This file system appears on the disk as pup_save.fs3 under Windows.

I'd like to get access to what's inside that file from within Windows so I can open and save things there. I found and installed Ext2 IFS which lets you mount Linux Ext2/Ext3 file systems in Windows, and gives you read/write access. (I'm guessing that because the file is named .fs3 that Puppy is using an Ext3 file system?)

The problem is that Ext2 IFS seems geared to partition based file systems. The GUI will let you mount an Ext2/3 partition, and shows all the partitions on my physical drives. I'm assuming that if I had a partition formatted in Ext3 I could just mount if from there.

But the file system I want to mount is not a partition - it's just a file! And I can't see any way in Ext2 IFS to select this file and mount it so that it will become accessible under Windows.

I'm probably missing something really basic here, but as I said I'm new at this. Could someone with a bit of Linux/Windows experience point me in the right direction? Thanks!

[40hz]

Hi:

The short answer is - you can't. 

You can't mount the Puppy file system because it doesn't exist in the same manner as it would if Puppy were installed on a real drive partition. It's being emulated by QEMU. The Linux 'drives' you're trying to mount don't 'exist' as Linux partitions unless QEMU-Puppy is running. The rest of the time they're just part of the data file used by QEMU.

The QEMU-Puppy website has a better writeup than I'm giving you. You might have missed it, so I'm quoting it below:

2.2. QEMU

From the site: "QEMU emulates a full system (for example a PC), including a processor and various peripherals. It can be used to launch different Operating Systems without rebooting the PC or to debug system code."

In other words: QEMU is a virtual machine. A virtual machine is a program that acts like computer hardware. In such a virtual machine, you can install an OS (Linux, Windows, BSD, whatever). This OS "sees" a processor, which is the real processor (I'm lying...), "sees" a hard drive, which is a big file on the host machine, "sees" a network card, which is emulated by QEMU, and so on. After shutting down the virtual machine, all that's left on the host (or USB memory stick) is just one big file: the virtual hard disk.

From the point of view of the host OS, QEMU is just a simple program which allocates a lot of memory, eats a lot of CPU cycles and opens and closes a couple of files. That's it.

When you think about it, you've answered your own question:

the file system I want to mount is not a partition - it's just a file!

Yup. That's exactly right.

[Jimdoria]

OK 40Hz - I think I've got it.

A question though - one of the reasons I went with QEMU Puppy is that it has the ability to boot "bare metal" Puppy Linux from the thumb drive. I've done this successfully. In this scenario (AFAIK) QEMU is not involved at all - it's just Puppy running. So Puppy must have the ability to access the volume file natively, outside of emulation.

I was guessing that using the .3fs file as a mountable storage volume was something you could generally do in Linux. There are analogs in the Windows world. TrueCrypt works the same way, mounting a single encrypted file as a storage volume.

Is this feature specific to Puppy Linux? That would explain why it isn't widely supported.

[40hz]

I'm not the world's greatest authority on Puppy (I mainly use it as a rescue OS for a non-bootable system) but I would guess it is unique to that distro.

Your best bet would be to go up on the forums and ask the real pros. Link for the main forum page can be found here:

http://www.murga-lin.../puppy/index.php?f=4

This thread might be of interest if you just want to boot from the USB but keep your files on a specific PC:

http://www.murga-lin...search_id=1413374969

BTW: Welcome to Linux!

[Armando]

Also Puppy Linux' author seems like a nice guy. He might be willing to help.

[f0dder]

Is the .3fs file a raw disk/partition image, or does QEMU itself add some structure information? That's pretty important... if it's raw, then you could use /dev/loop on linux to mount it, and theoretically the same could be done under windows (although the windows port of ext3fs probably only supports mounting partitions, not files).

Perhaps a usermode application like explore2fs supports opening files rather than partitions? (Haven't tried it, first google hit I found for "ext3 explorer").

[40hz]

There's a great article on how Puppy works up on the official website.

The direct link is: http://www.puppylinu...t/howpuppyworks.html

There was mention of using the explore2fs utility under Windows. Might be worth a try, although it seems to imply you might need to archive your data first.

From the Puppy website:

Updating and archiving

As you can see, Puppy consists of only 4 files. (actually, it is possible to have usr_cram.fs inside image.gz, reducing Puppy down to just 3 files -- the web download sites may have that configuration available. It is convenient for booting off a network to have just the two files vmlinuz and image.gz to worry about)

To update to the latest version of Puppy, you just need to get the latest vmlinuz, image.gz and usr_cram.fs. Updating is so very simple, but with v0.9.8 I made it even simpler by building an update option into the installation scripts. That is, boot up the latest live-CD and run the install-to-USB, install-to-Zip or install-to-hard-drive script and choose "update" rather than "new installation".

...but, it's so simple, you could do it manually if you wish.

Puppy does have a couple of archive programs, including one that I wrote that backs up only the changed files from /root each time. However, all your personal data, really, a snapshot of the entire the state of the system, is in the pup001 or pup100 file, so you can save a complete system snapshot just by making a copy of the pup001/100 file. Then compress it, like this (assuming the copy is named pup100-12dec04):

# gzip pup100-12dec04

and you will have pup100-12dec04.gz. Or use "zip" or "bzip2", Puppy has them all! Archive that anywhere you want.

You can mount an archived pup100 file at any time, and view its contents:

# losetup-FULL /dev/loop2 pup100-12dec04
# mount -t ext2 /dev/loop2 /mnt/data

You can also view the contents of pup100-12dec04 from Windows, by using the Explore2fs program. There is also a free native ext2 filesystem driver for Windows NT/XP.

http://uranus.it.swi...x/explore2fs-old.htm

[Jimdoria]

Thanks for the links. I also turned up Explore2fs. (I always google something before I post a question about it. Common netiquette!) Unfortunately, Explore2fs is read-only at the moment. Write access was removed due to instability and the author is not optimistic about it being added back anytime soon.

I definitely need R/W access or the whole point is moot, so that lets that out.

I'll see if I can post something over at the Puppy forums. I hesitate to post a Windoze question in a Linux forum, but I guess I'll just have do it, then dodge the rotten tomatoes. Thanks!

[ewemoa]

A shot in the dark may be, but...I noticed the following pieces of text on a page on VDK:

VDK can also open the following types of virtual disks:

Raw sector image which you can create with regular disk dump tools such as Linux dd command.
Non-partitioned disk image, such as floppy image, removable disk image, and dd image of a single partition. (This is not actually a type of virtual disk, but rather how the virtual disk is formatted.)
In this case, the whole image is treated as a single partition.

VDK is a disk driver, not a file system driver, therefore you can only access partitions which your Windows host can recognize. For example, you cannot access ext2 partitions on virtual drives unless you have a 3rd party ext2 file system driver installed on your Windows system.

So perhaps something useful can come about using VDK (or may be ImDisk) along with 'Ext2 Installable File System For Windows' / ext2fsd...

http://chitchat.at.i...o.jp/vmware/vdk.html
http://www.ltr-data....opencode.html#ImDisk
http://www.fs-driver.org/
http://www.ext2fsd.c...projects.htm#ext2fsd

[f0dder]

Oh, smart - so VDK is the windows analog of *u*x /dev/loop , basically?

[ewemoa]

 

so VDK is the windows analog of *u*x /dev/loop , basically?

-f0dder (October 15, 2008, 06:26 PM)

They do seem fairly similar.

I've been testing out ImDisk (not VDK) recently, and I'm definitely reminded of loop devices. 

FWIW, I noticed the following under 'Warnings and Limitations' on the aforementioned VDK page:

VDK does not communicate with Windows 2000/XP Mount Manager.
Therefore:

Disk Management Console (partition manipulation and mount point configuration) does not recognize the VDK virtual drives.
Many third party utilities, such as PartitionMagic, work fine.
Disk Defragment utility does not recognize the VDK virtual drives.
Many third party defrag utilities, such as Diskeeper, work fine.
Graphical mode of Check Disk may not work.
(command line chkdsk.exe works fine).

Perhaps eventually there will be out-of-the-box / more-integrated-with-OS support for something like VHD in a future version of Windows, but in the mean time, at least ImDisk is coming in handy for me