Live USB - persistent overlay issues

thewonderer57 · #1 9th April 2009, 01:11 AM

Hi there folks,

OK. I come as man in need. I want clarification of the idea of the persistent overlay on my USB stick, which has Fedora live KDE spin on it.

I first of all formatted my 16GB USB stick as FAT32. I then downloaded live-usb-creator 3.6.3. This was important because it removes the false limit of 2GB persistent overlays for FAT32 partitions. That's good. So I decide to use the GUI of the live-usb-creator to state 8GB for persistent overlay.

Now here's what I have. A USB stick with Fedora 10 KDE, with all packages updated, and OpenOffice, Firefox etc.. and the usual extras onto the USB.

There are a few things I just cannot get my head around. First of all, when I'm in Fedora booted from USB, I see that the file /mnt/live/LiveOS/overlay-Fedora has been set at just over 4GB. This does not change size, no matter how many packages I add/remove using YUM. The second strange thing is that, according to Firelight (images to come....), the capacity of my "/" mount is 8GB. This gives me a remainder of 4GB for /usr/share /usr/lib /var/tmp etc etc... I'm finding it very difficult to keep my "/" mount being below 100% capacity - a few times recently when attempting YUM installs, the rpm's in /var/tmp have filled up the 8GB in total, so I'm having problems.

To make this a lot clearer for you guys, I have made some screenshots for you, seen here:
http://linuxsoftwareblog.com/blog/?p=139

So I suppose I have a few questions:
1. How, exactly, does the system write to the overlay, and when?
2. Why has /mnt/live/liveOS/overlay-Fedora been set at 4GB? and how do I mount it to see how full in terms of files it is?
3. Should I just have set overlay to be the full 11.5GB the live-usb-creator offered me?
4. Was 8GB allocation too much ?
5. How can I resolve that I am using my 16GB USB pen effectively? i.e. Have enough room, and be flexible enough to have my music and videos in /home/liveuser and also to never hit an issue with YUM package installs or other writing to "/". ?

Your help is super useful to me, and I hope someone can clarify how I can make my setup more effective. If/when I get this to succeed, I will post a tutorial howto on the http://linuxsoftwareblog.com/?p=156 for the rest of the Fedora community !

thanks guys,

sideways · #2 9th April 2009, 01:23 AM

there's no point making the persistent overlay much bigger than the size of the root filesystem, which is 3GB on the F10 livecd, to check the size type 'df -hT /' in the live session. (to make it bigger you'd have to recreate the livecd from the kickstart file and change the 'part / --size xxxx' line near the top)

In any case, fat32 only supports 4GB max file size, so you wouldn't be able to create an 8GB overlay file.

Persistent overlays are unstable, instead, boot the livecd and install it on the usb pen, that way you can make your root filesystem as large as you want.

thewonderer57 · #3 9th April 2009, 01:35 AM

Hi sideways.

Wow! Thanks for the super quick response. And useful too. To be honest, I thought of that idea when I first of linux on usb sticks, but just could not and cannot find any real tutorial on the net on how to install to usb, insteaad just how to use live usb creator to use the usb as a live cd with a bit of overlay.

I love the idea of a native install onto usb. What are the prerequisites? Does the usb stick need to be formatted in to ext3 or fat32? I'd maybe need to format 4gb or so away to be a sotrage area for file transfers to windows pc's. If there is any official documentation for fedora full install to usb raather than a live usb then i'd love to see it.

If it can be done, again, I would write up the process for fellow fedora followers at http://linuxsoftwareblog.com/?p=156

Cheers.

sideways · #4 9th April 2009, 01:41 AM

The install to usb is done just as a normal hard disk install, but you select the usb disk as the target for the install and partition as you desire.

It is much slower to do the actual install, since writes on usb media are much slower than for a standard hard disk. But once installed it runs really well, just that large future yum updates are also slow. I have done this on a 8GB sdhc card for example which I boot in an eeepc netbook (one of the few netbooks that allow booting from sd cards)

One gotcha, is that grub may be confused about the labeling of the usb stick, during the install it may be hd1 (or sdb) but at boot it becomes hd0 (or sda), so will require manual fixing of grub.conf on the usb stick (so that root is hd0)

If you have problems, post back.

EDIT (Install grub on the mbr of the usb stick)

marko · #5 9th April 2009, 03:27 AM

Quote:

Originally Posted by thewonderer57

Does the usb stick need to be formatted in to ext3 or fat32? I'd maybe need to format 4gb or so away to be a sotrage area for file transfers to windows pc's. If there is any official documentation for fedora full install to usb raather than a live usb then i'd love to see it.

Cheers.

To avoid the 2GB limitation you have to use ext2/3 formatting, what you could do a make a small part of the key FAT32 and the majority of it ext2/3. Use the small FAT32 part for passing files back and forth to windows but the persistent volume would be on ext3 where it has to be to exceed 2GB

sideways · #6 9th April 2009, 03:30 AM

the limit in fat32 is 4GB not 2GB

And, anyway, as posted above, there is no point making the persistent overlay bigger than the root filesystem on the live image, which is 3GB in F10. (it was 4GB in F9)

thewonderer57 · #7 9th April 2009, 10:29 AM

Guys, thanks for this advise, a proposed solution within 12 hours is great.

I will reformat my USB pen using gParted when I get home from work:
16GB capacity
---------------
13GB - ext3
3GB - fat32

I will boot from the liveCD CD and target the 13GB ext3 partition for the install.

I will document the experience.

I'll let you know if I come across any problems.

thanks again to the both of you.

thewonderer57 · #8 9th April 2009, 11:50 PM

Well guys,

as promised, I have produced a howto tutorial on the basics on installing Fedora to a USB stick.

See it here:
http://linuxsoftwareblog.com/?p=156

Leave any feedback if you feel the need, it's very welcome !

thanks.

zackf · #9 10th April 2009, 12:12 AM

Great tutorial, did you have any issues with having to change grub like sideways mentioned above?

marko · #10 10th April 2009, 01:23 AM

Quote:

Originally Posted by sideways

the limit in fat32 is 4GB not 2GB

And, anyway, as posted above, there is no point making the persistent overlay bigger than the root filesystem on the live image, which is 3GB in F10. (it was 4GB in F9)

Be that as it may, but the limitation on the maximum on the old pre version 3.6 liveusb-creator persistent slider was 2GB and not 4GB for whatever reason.

sideways · #11 10th April 2009, 01:29 AM

Quote:

Originally Posted by marko

Be that as it may, but the limitation on the maximum on the old pre version 3.6 liveusb-creator persistent slider was 2GB and not 4GB for whatever reason.

maybe it formats as fat16, that does have 2gb limit, haven't used it for a while so don't recall.

zackf · #12 10th April 2009, 02:23 AM

Just to clarify the file size limitation is in fact 4GB for fat32, but the old versions of liveusb only allowed a persistent overlay of 2gb, so I think everyone is right. :-)