Moving system directories to a flash card

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== what is this page ==
 
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this page describes the setup on my own N800, I hope it can be useful to others, it surely helps me each time I update the system and I must remember what I had done.
 
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== why should you be reading this ==
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'''This method is ''not recommended'', as it is more fragile, and less usable than straight flash booting. Please use the steps for [[booting from a flash card]] instead!'''
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== Why move directories to a flash card ==
* you regularly run out of space while trying out new programs
* you regularly run out of space while trying out new programs
* you don't want to reflash /home each time you reflash your tablet
* you don't want to reflash /home each time you reflash your tablet
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* you want a LARGE /home partition
* you want a LARGE /home partition
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== what else you should consider ==
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== Alternative ==
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[[booting from a flash card]] describes a different method for solving the same above points.
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[[Booting from a flash card]] allows you to have your entire system running from a flash card, and thus to have your Home directory limited only by the size of the flash card.
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after trying it out I decided I would explore a different approach, where the internal memory would be used for the more volatile data (like /var and /tmp) and the flash card would be for the more static parts (as /usr and -to a lesser extent- /home).  I had read comments (link missing/required) about not being a good idea to run linux from a USB stick because of the limited lifetime of that kind of hardware so I thought I also did not want to run maemo from a low cost flash card.
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The reasons for doing this, rather than following the instructions here, are detailed in [[{{TALKPAGENAME}}| the discussion page]] of the page describing creating ext2 partitions for your tablet.
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an even safer approach is not doing any of these experiments and just enjoy your tablet as it is.
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This page details the steps the author followed to solve a problem, and represents his personal experiences.
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== needed ==
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It is strongly advised that if you have these issues, that you try [[booting from a flash card]].
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== Needed ==
* a working N800
* a working N800
* an internal flash card of 2Gigs or more.
* an internal flash card of 2Gigs or more.
* maybe a standalone linux desktop
* maybe a standalone linux desktop
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* one hour time and some [http://en.wikipedia.org/wiki/Roman_Chamomile chamomile]
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* one hour and some [[:wikipedia:Roman_Chamomile|chamomile]]
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== first time ==
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== First time ==
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=== partitioning ===
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=== Partitioning ===
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follow the steps on [[partitioning a flash card]], deciding how much space you want to reserve for /usr and how much for /home.
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[[Partitioning a flash card | Partition your flash card]], deciding how much space you want to reserve for /usr and how much for /home.
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on my system, I have slightly less that 0.5G for /usr and 1.5G for /home, respectively in partitions 2 and 3.  I have left a small 1st partition on the card because some hardware might otherwise think the flash card is corrupt and might want to "recover" it...   
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Suggested values for partition sizes are 500MB for /usr and 1.5GB for /home, respectively in partitions 2 and 3.  Leave a small FAT16 partition on the card in 1st position to prevent other systems considering that the card is corrupted and trying to "recover" it...   
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in general, it will not be a good idea to remove the card from the machine at any time and it will not be a good thing to put the card into anything else than your N800...
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It is suggested that you leave the card in your N800.
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=== copying your data to the new file systems ===
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=== Copying your data to the new file systems ===
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after you have created the partitions and have initialized them, mount them somewhere (for example /mnt/usr and /mnt/home) and copy /usr/* and /home/* there, keeping attributes
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After creating the partitions and initializing them, mount them at /mnt/usr and /mnt/home, and copy /usr/* and /home/* there, keeping file attributes:
  cp -a /usr/* /mnt/usr
  cp -a /usr/* /mnt/usr
  cp -a /home/* /mnt/home
  cp -a /home/* /mnt/home
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this will cost time so don't allow your N800 to die because of a low battery!
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Ensure your N800 is plugged in, since this operation will take some time.
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=== setting things up ===
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=== Setting things up ===
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after you have done this, I think the best way to go is reflashing your machine (apart from the above cp instructions, you also made a backup, didn't you?) and follow the steps in the next section.  this will clean up a lot of space on your internal memory.
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== after a reflash ==
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First, reflash your tablet, after carefully backing up any data you will need later, to free up space in internal memory and get back to factory settings.
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things might work also without a backup, but make one anyway, unless you trust me blindly and you want to test the procedure.
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Then use the Application manager to remove packages which are safe to remove. Some examples of packages which can safely be removed are the Maemo tutorial and documentation packages.
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short list of things to do:
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Boot the system with flash card in place, and ensure that your old data is there. To do this, [[Root access | become root]] and create a custom boot script which will mount partitions from your flash card:
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=== reflash the machine ===
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=== remove useless packages ===
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things like the tutorial and I can't remember what else...  I used the Application manager to remove everything which was removable.
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=== boot with flash card in place ===
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=== test your old partitions ===
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this needs a few more words
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after you have become root, do this:
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  #!/bin/sh
  #!/bin/sh
   
   
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  # register it for early execution
  # register it for early execution
  chmod +x /etc/init.d/mount_custom
  chmod +x /etc/init.d/mount_custom
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  cd /etc/init.d; for i in 2 3 4 5; do ln -s ../init.d/mount_custom /etc/rc$i.d/S15mount_custom
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  cd /etc/init.d; for i in 2 3 4 5; do ln -s ../init.d/mount_custom /etc/rc$i.d/S15mount_custom ; done
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=== reboot and check ===
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Now reboot and check that /mnt/usr and /mnt/home contain your data.
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now reboot and it's up to you how you want to check that /mnt/usr and /mnt/home contain what you expected
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You will need to re-copy your system files on top of your back-up of /usr to ensure a consisten system:
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=== new files to old /usr ===
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copy the new files from /usr to /mnt/usr
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  cp -a /usr/* /mnt/usr
  cp -a /usr/* /mnt/usr
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as for the first time, this too will take time so be patient and do not let your N800 suffer electricity hunger.
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As before, this will take time and plug in your tablet.
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Edit '''/etc/init.d/mount_custom''' again, setting '''MOUNT_ROOT=/''' and reboot if you dare.
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Your flash card partitions will now be mounted at /usr and /home, and will hide the system directories underneath.
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=== Restoring without a Backup ===
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In a bare N8x0 after a reflash you will see an empty menu. You need to re-configure repositories and re-install all the applications you had before.
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=== back to work ===
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After following this procedure, when you re-flash your tablet, you should still see all of your applications and personal data, since /usr and /home will not be affected.
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edit the '''/etc/init.d/mount_custom''' script setting '''MOUNT_ROOT=/''' and reboot if you dare.
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things should "just work" and if they don't then there's a mistake in the procedure so please let me know about it so we can correct it.
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However, even though applications will show up in the menu, many applications will be missing configuration files or other data required to run, and you will probably need to restore them from a back-up before using them again.
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=== more thoughts ===
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The list of applications which appears in the application menu will serve as a list of applications which you should re-install after a re-flash.
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most programs will not work out of the box and you should reinstall them (they are not marked as installed even if you will find them in your application menu).  I first started trying to use them and since some didn't work, I used the application menu as a list of things to reinstall.  it is more work than doing a backup so maybe doing a backup anyway would not be such a bad idea.  but this way I have cleaned up my repository list, which was quite messed up after that trouble with repostory/repository...
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=== Power Consumption ===
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the power consumption of the machine does go up this way and, more importantly, it will not be able to work once the charge is too low to read/write the flash cards. so this setup DOES shorten your autonomy...  I did consider stepping back, but a quick check on the usage of my /usr partition convinced me otherwise: even if I removed 30% of the installed programs I would still have zero space for user files.
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The power consumption of your tablet will be higher when using ext2 partitions on a Flash card, and your system will not work once the charge is too low to read/write the flash cards. This setup shortens your autonomy.
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[[Category:Midgard_wiki]]
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[[Category:N8x0]]
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[[Category:Users]]
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[[Category:Power users]]
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[[Category:Wiki page of the day]]
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Latest revision as of 21:02, 8 January 2011

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 This article is out-of-date, and needs to be updated.
Please see the talk page for discussion.


This method is not recommended, as it is more fragile, and less usable than straight flash booting. Please use the steps for booting from a flash card instead!

Contents

[edit] Why move directories to a flash card

  • you regularly run out of space while trying out new programs
  • you don't want to reflash /home each time you reflash your tablet
  • you would like the 'rwx' permissions logic also on the flash card
  • you want a LARGE /home partition

[edit] Alternative

Booting from a flash card allows you to have your entire system running from a flash card, and thus to have your Home directory limited only by the size of the flash card.

The reasons for doing this, rather than following the instructions here, are detailed in the discussion page of the page describing creating ext2 partitions for your tablet.

This page details the steps the author followed to solve a problem, and represents his personal experiences.

It is strongly advised that if you have these issues, that you try booting from a flash card.

[edit] Needed

  • a working N800
  • an internal flash card of 2Gigs or more.
  • maybe a standalone linux desktop
  • one hour and some chamomile

[edit] First time

[edit] Partitioning

Partition your flash card, deciding how much space you want to reserve for /usr and how much for /home.

Suggested values for partition sizes are 500MB for /usr and 1.5GB for /home, respectively in partitions 2 and 3. Leave a small FAT16 partition on the card in 1st position to prevent other systems considering that the card is corrupted and trying to "recover" it...

It is suggested that you leave the card in your N800.

[edit] Copying your data to the new file systems

After creating the partitions and initializing them, mount them at /mnt/usr and /mnt/home, and copy /usr/* and /home/* there, keeping file attributes: 

cp -a /usr/* /mnt/usr
cp -a /home/* /mnt/home

Ensure your N800 is plugged in, since this operation will take some time.

[edit] Setting things up

First, reflash your tablet, after carefully backing up any data you will need later, to free up space in internal memory and get back to factory settings.

Then use the Application manager to remove packages which are safe to remove. Some examples of packages which can safely be removed are the Maemo tutorial and documentation packages.

Boot the system with flash card in place, and ensure that your old data is there. To do this, become root and create a custom boot script which will mount partitions from your flash card: 

#!/bin/sh

# create the mount points for testing
mkdir /mnt/usr
mkdir /mnt/home

# create the startup script
cat > /etc/init.d/mount_custom << EOF
insmod /mnt/initfs/lib/modules/2.6.21-omap1/mbcache.ko
insmod /mnt/initfs/lib/modules/2.6.21-omap1/ext2.ko
MOUNT_ROOT=/mnt/
mount /dev/mmcblk0p2 ${MOUNT_ROOT}usr
mount /dev/mmcblk0p3 ${MOUNT_ROOT}home
EOF

# register it for early execution
chmod +x /etc/init.d/mount_custom
cd /etc/init.d; for i in 2 3 4 5; do ln -s ../init.d/mount_custom /etc/rc$i.d/S15mount_custom ; done

Now reboot and check that /mnt/usr and /mnt/home contain your data. You will need to re-copy your system files on top of your back-up of /usr to ensure a consisten system: 

cp -a /usr/* /mnt/usr

As before, this will take time and plug in your tablet.

Edit /etc/init.d/mount_custom again, setting MOUNT_ROOT=/ and reboot if you dare.

Your flash card partitions will now be mounted at /usr and /home, and will hide the system directories underneath.

[edit] Restoring without a Backup

In a bare N8x0 after a reflash you will see an empty menu. You need to re-configure repositories and re-install all the applications you had before.

After following this procedure, when you re-flash your tablet, you should still see all of your applications and personal data, since /usr and /home will not be affected.

However, even though applications will show up in the menu, many applications will be missing configuration files or other data required to run, and you will probably need to restore them from a back-up before using them again.

The list of applications which appears in the application menu will serve as a list of applications which you should re-install after a re-flash.

[edit] Power Consumption

The power consumption of your tablet will be higher when using ext2 partitions on a Flash card, and your system will not work once the charge is too low to read/write the flash cards. This setup shortens your autonomy.

Retrieved from "http://wiki.maemo.org/Moving_system_directories_to_a_flash_card"