#Creating a uSD image from a file tree  

<abstract>
This article illustrates how to create a bootable Linux microSD image
starting from a file tree
</abstract>

Sometimes could be useful to create a uSD bootable image starting directly from the
file tree generated by [Debian Multistrap](/debian_stretch) scripts.

A bootable image can be distributed directly to Mac or Windows users those can generate in this way bootable uSD even if they cannot write in ext4 format directly.

##Step by step procedure

Create a regular file as large as the total size of your file tree. In this example we will create a 1GB file:

<pre class="terminal">
$ <b>dd if=/dev/zero of=myimage.img bs=512 count=1953125</b>
1953125+0 records in
1953125+0 records out
1000000000 bytes (1.0 GB) copied, 1.80442 s, 554 MB/s
</pre>

Associate the first free loop device (-f option) to the regular file and show the loop device used (--show option):

<pre class="terminal">
$ <b>sudo losetup -f --show myimage.img</b>
/dev/loop0
</pre>

Create two partitions:

<pre class="terminal">
$ sudo parted -s /dev/loop0 mklabel msdos
$ sudo parted -s /dev/loop0 mkpart primary fat32 4 128
$ sudo parted -s /dev/loop0 mkpart primary ext4 128 100%
$ sudo parted -s /dev/loop0 set 1 boot on
$ sudo parted -s /dev/loop0 print
$ sudo partprobe /dev/loop0
$ sudo kpartx -s -a /dev/loop0
</pre>

Create the filesystems inside the partitions:

<pre class="terminal">
$ sudo mkfs -t vfat -n boot /dev/mapper/loop0p1
$ sudo mkfs -F -t ext4 -L rootfs /dev/mapper/loop0p2
$ sync
</pre>

Mount the new filesystems:

<pre class="terminal">
$ mkdir mnt
$ mkdir mnt/boot
$ mkdir mnt/rootfs
$ sudo mount -t vfat /dev/mapper/loop0p1 mnt/boot
$ sudo mount -t ext4 /dev/mapper/loop0p2 mnt/rootfs
</pre>

Now copy the file tree inside mnt/boot and mnt/rootfs

Then umount the disks type:

<pre class="terminal">
$ sudo umount mnt/boot
$ sudo umount mnt/rootfs
$ sudo losetup -d /dev/loop0
$ sync
</pre>

Now the myimage.img file is ready to be written on uSD card

<pre class="terminal">
$ sudo dd if=myimage.img of=sdb
</pre>



##Link

* [Volumio script to generate boot images](https://github.com/volumio/Build/blob/master/scripts/pine64image.sh)


@include='bio_tanzilli'