This tutorial explains the steps we use to prepare iso images of our systems, ready to be duplicated on multiple raspberry pi. It is useful to have some knowledge in linux tools to manipulate partitions and filesystems. This tutorial will give you a basic knowledge of this tools, throught making the boot SD card and the system usb card.
We use a SD card to boot, and a usb key for the system. We beliebe in this solution for two reasons:
- SD cards are not meant to be used for long-term multiple read & write operations, usb key are better for this. This means that the SD card can have corrupted data after some time.
- copying 3 GB on 64 SD cards is very long. It's faster to copy the boot partition (63 MB) on 64 SD cards, and then copy the system (3 GB) on 64 usb keys with multiple usb hubs to copy in parallel.
sudo apt-get install pv
We are going to use usb and sd partition on your hard drive, beware that you an damage your partition if you write on the wrong disk. To know what disk to edit run
df -h
it will list available disks.
In this tutorial we will assume that your SD card is on /dev/mmcblk0 and your usb key on /dev/sdb.
Yours should be different. Take care when copy/pasting.
We will modify two things: partitions and filesystems, two different things. Check the links at the end of the tutorial if you are not familiar with the two concepts.
Get a raspbian iso image from the raspberry pi foundation , clone it on a sd card using this steps
umount /dev/mmcblk0
sudo dd bs=4M if=/path/to/raspbian.iso | pv | dd of=/dev/mmcblk0
sync
Try this sd card on a raspberry pi and make sure it is working as expected.
Insert back the SD card in your computer. Edit the boot partition to startup with the usb key instead of partition 2 of SD card, with this line:
sed -i 's/root=\/dev\/mmcblk0p2/root=\/dev\/sda1/' /path/to/mounted/p0/boot/cmdline.txt
And then create an iso image
umount /dev/mmcblk0p1
umount /dev/mmcblk0p2
sudo dd bs=4M count=16 if=/dev/mmcblk0 | pv | dd of=boot.iso
Insert an other SD card and
umount /dev/mmcblk0
sudo dd bs=4M if=boot.iso | pv | dd of=/dev/mmcblk0
sync
umount /dev/mmcblk0p1
umount /dev/mmcblk0p2
sudo dd bs=4M if=/dev/mmcblk0 | pv | dd of=snapbox.iso
sync
Setup the image via loopback
sudo losetup -f --show snapbox.iso
Note the loop where it is setup, like /dev/loop23
sudo fdisk -l /dev/loop23
Result:
Disk /dev/loop23: 14,9 GiB, 15931539456 bytes, 31116288 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disklabel type: dos
Disk identifier: 0xce513368
Device Boot Start End Sectors Size Id Type
/dev/loop23p1 8192 137215 129024 63M c W95 FAT32 (LBA)
/dev/loop23p2 137216 31116287 30979072 14,8G 83 Linux
Note the start sector of p2 (137216) to setup it
sudo losetup -f -o $((137216*512)) --show snapbox.iso
Result: /dev/loop24
And mount
sudo mkdir /mnt/iso
sudo mount /dev/loop24 /mnt/iso
Get the size of partition
df
Result:
Filesystem 1K-blocks Used Available Use% Mounted on
dev 8147152 0 8147152 0% /dev
run 8150752 1348 8149404 1% /run
/dev/sda6 30832636 25923332 3320056 89% /
tmpfs 8150752 380204 7770548 5% /dev/shm
tmpfs 8150752 0 8150752 0% /sys/fs/cgroup
tmpfs 8150752 360 8150392 1% /tmp
/dev/sda7 113873536 104152548 3913476 97% /home
/dev/sda1 262144 24804 237340 10% /boot/efi
tmpfs 1630148 16 1630132 1% /run/user/120
tmpfs 1630148 28 1630120 1% /run/user/1000
/dev/loop24 15216784 2466812 12102196 17% /mnt/iso
Note the total size used (2466812) and add a bit more space you need for runtime execution or additional programs to install later. Here we will use 2700000.
sudo umount /dev/loop24
sudo fsck -f /dev/loop24
sudo resize2fs -f /dev/loop24 $((2700000/4))
Remount it to make sure everything went fine.
sudo mount /dev/loop24 /mnt/iso
ls /mnt/iso
sudo fdisk /dev/loop23
Press 'd' to delete partition, the '1', then 'd' again to delete the second partition. Create a new one with 'n', and select primary and partition number 1 First sector, 2048. Last sector is the total size, by default, it is the last one: 31116287 We will do the math to shrink this in an other window:
echo '2700000*2 + 2048' | bc
Enter the result back in fdisk And then, type 'w' to write, ctrl+D to exit
Setup this new partition
sudo losetup -f --show -o $(echo "2048*512" | bc) snapbox.iso
Copy the content of the old one to this new partition
sudo dd if=/dev/loop24 of=/dev/loop25
Mount it to make sure everything went fine.
sudo mkdir /mnt/iso2
sudo mount /dev/loop25 /mnt/iso2
ls /mnt/iso2
Do the math
echo '2700000 + (2048/2)' | bc
And apply
truncate -s 2701024K snapbox.iso
Mount it to make sure everything went fine.
sudo mkdir /mnt/iso3
sudo losetup -f --show -o $(echo "2048*512" | bc) snapbox.iso
sudo mount /dev/loop28 /mnt/iso3
ls /mnt/iso3
umount /dev/sdb0
sudo dd bs=4M if=snapbox.iso | pv | dd of=/dev/sdb
sync
And then try this usb key with the boot SD card you made earlier.
Voilà!
If you need to expand the filesystem because you lack space, it is easy to do it directly on the raspberrypi. raspi-config won't do it because it looks for a SD card. But you can do it this way
sudo fdisk /dev/sda
- press 'd' to delete the partition,
- press 'n' to make a new one, and select
- press enter for primary,
- press enter for number 1,
- press enter for first sector 2048,
- press enter for default, to expand to the max size on usb key, or enter the new size you need for the last sector.
- press 'w' to write changes
Then
sudo reboot
sudo resize2fs /dev/sda1
Check it did the job:
df -h
Helpful links: http://sirlagz.net/2013/03/04/how-to-resize-partitions-in-an-image-file-part-2/ http://www.cyberciti.biz/tips/understanding-unixlinux-file-system-part-i.html