28 replies to this topic

[LavaChild]

Hi there,

Is it possible to to run in a "READ ONLY" state? Eg, any modifications to files are NOT retained after a reboot?

I often let people look at my EEE PC (Gets alot of attention) however after spending so long working on getting my EEE PC just how I want it I am rather worried that they will change things, etc. I have a back up of my installation so it is no real difficulty in rolling back every time somebody uses it... But what a pain!!

It would also be useful for me - Many times I turn the EEE PC on simply to check the internet... It would be great if I could turn on and know that there is no way anything can get damaged (Ideally even stuff like temp net would not survive a reboot!).

It would be absolutely fantastic if this were possible... How can it be done? I was wondering if it could be done via the grub menu (Have an entry for "Read Only Mode")...

Cheers.

[eeecat]

There are two filesystems that are mounted with "unionfs" (see wiki for more info). One is read/only, and the other "read/write" which gets all the changes. If you could take your "known good" configuration with all your tweaks (set of files on the "read/write" filesystem) and copy them onto the "read/only" filesystem underneath (you'll have to do this in single user mode or after booting an external USB OS or something like that). Then you just start with an empty read/write partition. Let people do whatever they like to the box, then you can trivially restore it with the F9 boot.

[albkwan]

There are 2 ways to do this:

1) For read only state, you can tweak your eeepc to boot in RAM mode. See this wiki: http://wiki.eeeuser.com/ram_mode

2) For show it to your friends, you can boot your eeepc with the USER partition mounted on a SDHC as described in this thread: HOWTO - Mount SD card as part of the unionfs.

[LavaChild]

Hi there,

Thanks for both replies.

albkwan -
2) I'd rather not do (Constantly have an SD card in for other purposes).
1) Sounds worth a shot... Had a go but when I've finished in rescue mode I cannot "exit" out as it gives me the error "Kernel panic - not syncing: Attempting to kill init!" amongst other errors. I have to power off but holding power button. Pressing F9 my entry is there however I can an error and booted in busybox. Error is: "mount: Mounting /dev/sda1 on /mnt-system failed: No such file or directory
Could not mount OS on /dev/sda1. Starting debugging shell..."
Any ideas?
Even if I do get this to work the Wiki mentions "Every time you boot into this mode it will act like a first time boot." - Does this mean that my "mods" and "tweaks" (Eg, start menu and such) will never work in this mode? If so - Not a good solution (For my needs) in any case.

eeecat:
I believe that I understand what you are saying but am not sure I understand how I would go about this. How would I go about ensuring that *all* files are moved into the "perminant" mount and *nothing* is left (initially) on the other mount? Also, if I did this - Upon using the F9 would I still be prompted to create my user account again (Undesirable) or would it simply load into my "previously saved state"?

Has this method been tried before? I've little linux knowledge but relatively good with computers and picking it up as I go so I don't mind trying this if I'm sure of success (Or at least somebody else having had success...) - Don't want to be the test bed though!

Also, I back up my EEE PC using the method outlined in this thread:
http://forum.eeeuser...pic.php?id=4281

If I were to backup like this and at a later date decide I do not like using the F9 method as my own personal restore and prefer it how it is by default, would rolling back my image (As outlined in that thread) also roll back the original way of F9'ing or would this be a perminant (Until format) solution?

Cheers both!

[albkwan]

Quote

1) Sounds worth a shot... Had a go but when I've finished in rescue mode I cannot "exit" out as it gives me the error "Kernel panic - not syncing: Attempting to kill init!" amongst other errors. I have to power off but holding power button. Pressing F9 my entry is there however I can an error and booted in busybox. Error is: "mount: Mounting /dev/sda1 on /mnt-system failed: No such file or directory
Could not mount OS on /dev/sda1. Starting debugging shell..."
Any ideas?

If you can still boot into the stock distro, probably your new initramfs image is not packed correctly. Try do it again.

If however you cannot boot into the stock distro now, probably you are having a filesystem error on /dev/sda1. You will need to run a filesystem check on it. This is tedious, because you cannot fsck from within the OS itself when sda1 is mounted. So, the easy way is to have something like a Puppy Linux on a flash disk to do this.

Quote

Even if I do get this to work the Wiki mentions "Every time you boot into this mode it will act like a first time boot." - Does this mean that my "mods" and "tweaks" (Eg, start menu and such) will never work in this mode? If so - Not a good solution (For my needs) in any case.

Yes, you are right. Only things from factory will remain unless you manually move them from sda2 to sda1.

So in your case, probably you will need a custom initramfs image that mounts both sda1 and sda2 as read only, and then a RAM disk as read write. Theoretically, this is possible. But I have not done this before.

May be something like this in init:

...
if ! mount -t ext3 -o ro /dev/sda2 /mnt-user; then
    echo Error mounting user partition. Must run filesystem scan!
    exec switch_root /mnt-system /sbin/scanuser.sh
fi 

mkdir /mnt-ram
if ! mount -t tmpfs -o rw user /mnt-ram; then
    echo Error mounting tmpfs as RAM disk partition. 
fi
...
mount -t unionfs -o dirs=/mnt-ram=rw:/mnt-user=ro:/mnt-system=ro unionfs /mnt
...

[LavaChild]

HI there,

Thank you *very* much for all replies.

I believe now I have a solution that will suit my needs well! All that needs doing is if somebody can confirm it is okay and some help in achieving it!

Now that I am happy for now with my setup can I copy EVERYTHING over to sda1 leaving sda2 *completely* empty? This will then allow me to do two things: a) F9 back to my "backed up - working" state b) Allow people to use my "normal" boot up but on "ramfs" meaning they get effectively the same as me but can do no damage that will not be sorted on a reboot.

If this is possible could somebody please advise exactly how to do this - Any easy way in rescue console to move all files over? Will sda2 then need formatting? Will either partition need resizing/etc for this to work?

Finally, as before, I back up using "dd if=/dev/sda of=/media/bigdisk/eee-disk-image" and I roll out the back up using "dd if=/media/bigdisk/eee-disk-image of=/dev/sda". If I were to back up like this BEFORE attempting these changes would all of these changes be reversed (Say, I was not happy with the results) if I were to roll the back up in this manner? Does this back up monitor changes in sda1, for example?

Cheers.

PS - re: RAM mode problem, I can still boot into the normal Xandros distro fine... Just RAM mode that doesn't work. Have tried twice now and same each time. Only thing I can think of is the command "find . | cpio -o -H newc | gzip > /boot/initramfs-ram_mode.img" wont run so I do "sudo bash" and then the command. This any reason for problems?

[albkwan]

Correct me if I am wrong:

Although I have not tested this actually building an initramfs image, I think the instruction in the wiki is wrong. The command:

mount -t tmpfs -o rw user /mnt-user

has specified the device as "user" which is strange.

What I have been using for my RAM mode is:

mount -t tmpfs tmpfs /mnt-user

and I know this works.

Anyone else can confirm this?

Edited by albkwan, 30 January 2008 - 11:45 AM.

[albkwan]

Lavachild,

I have tested this sda1+sda2+RAM mode. Really like this idea! :)

It works! It boots up with all the modifications and tweaks still there, and files I write to "My Documents" disappear after re-boot.

However, due to unknown reason, USB is not working. Not sure if this is an old problem because I have not used sda2 for long time already (because I have been using a 4G SDHC as the USER partition to have more working space). Will check further on this.

To do this, the steps are just as same as the wiki, only replace the init file with the following:

UPDATE:
Have done this with sda1 (read only) + sdb1 (read only) + RAM disk (read/write). Works perfect!

I am thinking we can also use this method to test installing new software. For example, Asus Add/Remove Software that is becoming very dangerous now!

#!/bin/sh
mount -t proc proc /proc

ROOT=`cat /proc/cmdline | sed 's/.*root=// ; s/ .*//'`

mount -t ext2 -o ro $ROOT /mnt-system
if [ $? -ne 0 ] ; then
    echo Could not mount OS on $ROOT. Starting debugging shell....
    /bin/busybox sh
fi

if ! mount -t ext3 -o ro /dev/sda2 /mnt-user; then
    echo Error mounting user partition. Must run filesystem scan!
    exec switch_root /mnt-system /sbin/scanuser.sh
fi 

mkdir /mnt-ram
if ! mount -t tmpfs tmpfs /mnt-ram; then
    echo Error mounting tmpfs as RAM disk partition. 
fi 

mount -t unionfs -o dirs=/mnt-ram=rw:/mnt-user=ro:/mnt-system=ro unionfs /mnt
if [ $? -ne 0 ]; then
    echo Could not mount unionfs. Starting debugging shell....
    /bin/busybox sh
fi

mount --move /mnt-system /mnt/mnt
umount -l /mnt-user
umount -l /mnt-ram

umount /proc

if [ -n "$INIT" ]; then
    if [ -n "$XANDROSBOOTDEBUG" ]; then
    exec switch_root /mnt $INIT </mnt/dev/console >/mnt/dev/console
    else
    exec switch_root /mnt $INIT </mnt/dev/null >/mnt/dev/null
    fi
else
    exec switch_root /mnt /sbin/fastinit "$@" </mnt/dev/console >/mnt/dev/console
fi

echo 
echo Init Failed. Starting emergency shell....
/bin/busybox sh

Edited by albkwan, 30 January 2008 - 01:52 PM.

[LavaChild]

Hi there,

Thank you so much for so much dedication to this problem.

Using your script I have got ramfs working. It also adds sda2 read only as well. You say your script adds sdb1 read only as well. What is sdb1? If sdb1 is the SD card I do not wish for ramfs to even *SEE* this... What code (From your above) do I remove to remove this?

Finally, I found that when entering the code you gave above there was alot of stuff I deleted (So it matched yours) - Some stuff about XANDROSBOOTDEBUG, etc, etc. Is it necessary to remove those bits?

Cheers.

[albkwan]

Quote

Using your script I have got ramfs working. It also adds sda2 read only as well. You say your script adds sdb1 read only as well. What is sdb1? If sdb1 is the SD card I do not wish for ramfs to even *SEE* this... What code (From your above) do I remove to remove this?

The script I gave above is only for sda1+sda2. For sdb1, you will need to load also USB drivers. That's another script.

Quote

Finally, I found that when entering the code you gave above there was alot of stuff I deleted (So it matched yours) - Some stuff about XANDROSBOOTDEBUG, etc, etc. Is it necessary to remove those bits?

Those stuffs are not necessary if you boot in RAM mode. You can always access them with the default initramfs image.

[LavaChild]

Hi there,

I'm curious now - Seems like a real tidy package. Any chance you could please post your script for the USB support and explain how I implement it?

Also, I want to as described in post number two, copy all of the current contents of my sda2 into sda1 so that if I'm on the road (Not in RAM mode...) and for some reason I "break" my EEE PC, I'd like to be able to press F9 and get everything back. With my *very basic* linux knowledge I simply tried to copy all files over in Rescue Console (Don't even know if this is correct but I tried mv /sda2/* /sda1/*) - Some problems with this... Some files it said were unable to be copied (Not a clue!)... sda1 ran out of space (I'd imagine the partiation needs resizing...).

Could you please help me as best possible in transferring *all* files into sda1 (Making the partition ONLY as large as it needs to be - Don't want to waste any space), leaving sda2 empty? Could you also explain any "best practises" I should stick to (Eg, should I at any time do the Windows equivilent of "Disk Defragment" or "Scan Disk"... Should I "format" sda2 after copying files to ensure it is COMPLETEY empty?

I look forward to hearing from you. A working RAM mode (With ro sda1, sda2 [And maybe even ro sdb1]) and a backup solution on F9 with my present working OS would be absolutely fantastic... A real road warrior!

Cheers! (Alot! :D)

EDIT: Also not too familiar with linux filesystems... All these ext2 and ext3!! Whilst I'm at it, am I best to change any of the filesystems? Or are they currently best suited as they are? If I should change which drives should I change to what and how? Cheers again! :)

Edited by LavaChild, 31 January 2008 - 10:04 AM.

[albkwan]

Quote

Could you please help me as best possible in transferring *all* files into sda1 (Making the partition ONLY as large as it needs to be - Don't want to waste any space), leaving sda2 empty?

Up to now, we do not know of any easy and simple method to do this. The .whxxxxxxx files of the unionfs are rather complicated. See this wiki: howto:makechangespermanent for some idea.

I do have some success moving files from the USER partition to the SYSTEM partition. But you really need to know what files you want to move, which is the correct one, etc. So, there is no simple instruction I can offer to you.

Quote

Any chance you could please post your script for the USB support and explain how I implement it?

Use the script below. You will also need to build a device for sdb1 in your init RAM filesystem as per step 6 of this thread. If you want more information, you can take a look at my webpage.

init for mounting sda1 + sdb1 + RAM disk as unionfs:

#!/bin/sh
mount -t proc proc /proc

ROOT=`cat /proc/cmdline | sed 's/.*root=// ; s/ .*//'`
VERSION=`cat /proc/version | cut -f3 -d" "`

mount -t ext2 -o ro $ROOT /mnt-system
if [ $? -ne 0 ] ; then
    echo Could not mount OS on $ROOT. Starting debugging shell....
    /bin/busybox sh
fi

#load USB modules
insmod -f /mnt-system/lib/modules/$VERSION/kernel/drivers/usb/core/usbcore.ko
insmod -f /mnt-system/lib/modules/$VERSION/kernel/drivers/usb/host/ehci-hcd.ko
insmod -f /mnt-system/lib/modules/$VERSION/kernel/drivers/usb/host/uhci-hcd.ko
insmod -f /mnt-system/lib/modules/$VERSION/kernel/drivers/usb/storage/libusual.ko
insmod -f /mnt-system/lib/modules/$VERSION/kernel/drivers/usb/storage/usb-storage.ko

#loop scanning for USER partition on SD card
while ! grep -q "sdb1" /proc/partitions; do sleep 1; done

if ! mount -t ext3 -o ro /dev/sdb1 /mnt-user; then
    echo Error mounting user partition. Must run filesystem scan!
    exec switch_root /mnt-system /sbin/scanuser.sh
fi 

mkdir /mnt-ram
if ! mount -t tmpfs tmpfs /mnt-ram; then
    echo Error mounting tmpfs as RAM disk partition. 
fi 

mount -t unionfs -o dirs=/mnt-ram=rw:/mnt-user=ro:/mnt-system=ro unionfs /mnt
if [ $? -ne 0 ]; then
    echo Could not mount unionfs. Starting debugging shell....
    /bin/busybox sh
fi

mount --move /mnt-system /mnt/mnt
umount -l /mnt-user
umount -l /mnt-ram

umount /proc

if [ -n "$INIT" ]; then
    if [ -n "$XANDROSBOOTDEBUG" ]; then
    exec switch_root /mnt $INIT </mnt/dev/console >/mnt/dev/console
    else
    exec switch_root /mnt $INIT </mnt/dev/null >/mnt/dev/null
    fi
else
    exec switch_root /mnt /sbin/fastinit "$@" </mnt/dev/console >/mnt/dev/console
fi

echo 
echo Init Failed. Starting emergency shell....
/bin/busybox sh

[LavaChild]

Hi there,

Thank you so much for your help :) You've really been incredibly helpful... A credit to the EEE PC moddin' community!

Due to my limited knowledge, and your advise, I will hold out moving all files into sda1 for now: None the less I thank you for taking the time to explain!!

What I WILL do now, however, is (And only this...) make the RAM Mode, as we've previously discussed. Just one thing I'd like to check here (As I'd rather get it done first time and happy ever after [Waste no more of your time either!!]). In your previous message you say "You will also need to build a device for sdb1 in your init RAM filesystem as per step 6 of this thread.".

If, when I modify my init file (After unpacking the .img) I simply just delete its contents and paste the stuff you have given me (At the bottom of your post) do I *still* need to do something else? Or do I need to do this AND "build this device". If so... Can you please be more specific how I do this. The other thread says:

"
cd /mnt/sdb1/boot/temp/dev
mknod -m 660 sdb1 b 8 17
"

I'm not sure I understand this command.

Many Thanks. :)

EDIT: If I'm correct (Please confirm :)) sdb1 will be my (perminantly) inserted SD card. This works in the previous posted RAM Mode. I also tried connecting a USB pen drive and this also inserted fine. I do not know if these are read/write or read only (I think read only would be preferable). Could you please explain what the difference is between the first RAM Mode you posted and this second one? Sorry for being a pain but ALMOST there - Please hang in there :)

EDIT#2: In order to research this myself (I'm not somebody that simply asks many questions and expects all answers without any work!) I've been reading your webpage, as advised. More specifically "INIT for boot Xandros from USB on the Eeepc". Here is mentions versions both with and without unionfs. Please note that I DO have unionfs and *do not* intend to remove it. Could you please confirm that the scripts you have given above *are* designed with a user whose unionfs remains in place? Cheers (For the millionth time!! Heh).

Edited by LavaChild, 31 January 2008 - 07:26 PM.

[albkwan]

Quote

In your previous message you say "You will also need to build a device for sdb1 in your init RAM filesystem as per step 6 of this thread.".

This is only required if you intend to mount also your SD as part of the unionfs.

Quote

If, when I modify my init file (After unpacking the .img) I simply just delete its contents and paste the stuff you have given me (At the bottom of your post) do I *still* need to do something else? Or do I need to do this AND "build this device". If so... Can you please be more specific how I do this. The other thread says:

"
cd /mnt/sdb1/boot/temp/dev
mknod -m 660 sdb1 b 8 17
"

If you only intend to mount sda1 + sda2 + RAM disk, then no need to add this device node.
If you intend to mount also SD as part of the unionfs. Then you have to create a mounting point for it.

Quote

Could you please explain what the difference is between the first RAM Mode you posted and this second one?

The first RAM mode is sda1+sda2+RAM.
The second RAM mode is sda1+sdb1+RAM

The difference between them is that for SD and USB flash disk, you have to insert the USB modules into the kernel for it to detect the USB devices before you mount them.

Pls note that SD are always sdb for Xandros. And if you only have 1 flash drive, then it will be sdc.

Quote

I do not know if these are read/write or read only (I think read only would be preferable).

Whether they will be mounted as read only (ro) or read/write (rw) depends on this command

mount -t unionfs -o dirs=/mnt-ram=rw:/mnt-user=ro:/mnt-system=ro unionfs /mnt

In this example:
/mnt-ram=rw
/mnt-user=ro
/mnt-system=ro

Also, the branch that appears first in the command will have the highest priority. i.e. If a file named foo is found in all 3 branches, the unionfs kernel will read the one from /mnt-ram and ignore the other 2 in /mnt-user and /mnt-system. And if the file foo is only found in, say /mnt-system, then it will copy it into /mnt-ram and edit it there. So, nothing is saved when you reboot because /mnt-ram is in RAM disk.

Unfortunately, there is no easy way to check whether the branches have been mounted ro or rw (except sda1 which can be seen in /etc/mtab). What I do is to boot from USB and examine the contents of each branch to verify any files got written into it.

Quote

Could you please confirm that the scripts you have given above *are* designed with a user whose unionfs remains in place?

Yes, steps I gave above are all for working with unionfs. Without the unionfs, you can not overlay filesystems like this.

Hope you enjoy all these tweaks :)

[LavaChild]

Hi there,

Being as I use my SD and USB drive *just* as removable storage (Not as part of the file system as such) therefore I think, now you've explained it, that the first script you posted is the correct one for me.

I've already completed it once however that was after having messed around with the file system a little too much! Will roll back from one of my backups soon (Hopefully later this evening) and *fingers crossed* I'll be able to reply that it's all worked well!

In advanced, thank you very much for all of your help... I've EXACTLY what I wanted (From what I've seen so far) from RAM mode... And have a much better understanding to sort out moving my files into sda1 at a later date.

Cheers!

[LavaChild]

Just a follow up: Just applied the changes and everything is working *perfectly*. Really pleased! A credit to the EEE PC community...

Somebody, this needs adding to the Wiki (With correct credit to albkwan).

Cheers again :)

[zeroid]

I've just installed ram-mode and now have this as the default boot choice to ensure nothing can get messed up. My documents and firefox profile is on the SDHC so this works really well for me.

Can anyone tell me how I can view all the changes that have been made to the file system in the ramdisk? You could do this using the standard unionfs setup simply by mounting sda2 somewhere and taking a look.

Maybe by removing the lazy umount line in init (umount -l /mnt-user or something) - would that leave it so that I could see all the changes in /mnt-user?

[albkwan]

For sda2, because it is a physically existing device, you can always mount it anytime anywhere. But the RAM disk is non-existent. Unless you can tell the kernel whereabout is this RAM disk.

I think removing the line (umount -l /mnt-user) is not enough. As the mounting point (/mnt-user) will be gone after you switch_root. So you should also "mount --move /mnt-user [newdir]", where [newdir] should be somewhere in the root filesystem of your unionfs.

[zeroid]

I had a weird problem since enabling ram mode - I can no longer boot in normal mode, but I can still boot in ram mode.

I had initially removed unionfs and converted sda1 to ext3. The normal entry in my grub menu mounts sda1 as ext3 and there is no unionfs. The ram mode entry mounts sda1 as ext3 read-only and unionfs on tmpfs as described in the wiki.

I booted into normal mode last night to make some changes to the touchpad settings (which incidentally didn't seem to stick after a further reboot). Somewhere along the way, normal mode no longer boots up it never gets to the desktop but instead seems to be in a loop between the various black screens you get before the desktop appears.

Boot into ram-mode however and everything is fine. How can this be?

Luckily I do have a backup from before I converted to ext3, but how can I find out exactly what went wrong?

[albkwan]

Quote

I had a weird problem since enabling ram mode - I can no longer boot in normal mode, but I can still boot in ram mode.

I had initially removed unionfs and converted sda1 to ext3. The normal entry in my grub menu mounts sda1 as ext3 and there is no unionfs. The ram mode entry mounts sda1 as ext3 read-only and unionfs on tmpfs as described in the wiki.

I booted into normal mode last night to make some changes to the touchpad settings (which incidentally didn't seem to stick after a further reboot). Somewhere along the way, normal mode no longer boots up it never gets to the desktop but instead seems to be in a loop between the various black screens you get before the desktop appears.

Boot into ram-mode however and everything is fine. How can this be?

Luckily I do have a backup from before I converted to ext3, but how can I find out exactly what went wrong?

You mean you can boot up to both normal mode and ram mode before you convert to ext3. Am I right? Then everything is still working except the initramfs image for the normal mode.

Have you edit the "init" in the initramfs image for the normal mode and change it to mount $ROOT as ext3?

mount -t ext3 -o rw,noatime $ROOT /mnt