The official images supplied are raw disk images, which could have been created using dd.
How do I make an image bigger? I'm not interested in repartitioning said image as that has already been answered in How can I resize my / (root) partition?.
asked Jul 12, 2012 at 8:34
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Not exactly sure what you mean by expanding. Are you looking to perform the 'resizing of the partition' on the image before dd'ing it to the disk?– JoostJul 12, 2012 at 8:52
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That is one goal, but in order to do that, one must expand the disk image.– Alex ChamberlainJul 12, 2012 at 8:55
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2 Answers
As explained in this question there are two methods of expanding the image. Below are two examples to expand the file by 1 kilobyte.
DD creates a non-sparse file
dd if=/dev/zero bs=1k count=1 >> myimage.img
Truncate creates a sparse file
truncate -s +1024 myimage
You probably want to use truncate. A sparse file only writes the metadata of the blocks it uses, instead of actually writing the blocks. This makes creating the file faster (as it does not have to write actual zero's to the disk) and it saves space on your disk.
Note Apple's HFS+ filesystem does not support sparse files.
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If supporting sparse files is a requirement for POSIX i guess not. Here is a nice demonstration of the differences between HFS+ and some ext (i guess) stackoverflow.com/a/193015/689893. Appearently it does creates the file but it uses disk space like it's a normal file instead of a sparse file.– JoostJul 12, 2012 at 9:54
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A sparse file does contain data, so i guess you can just add zeroes. It will handle that part as non-sparse.– JoostJul 12, 2012 at 10:32
An incredibly easy way of resizing the image is to use one of the qemu tools called qemu-img. This of course depends on the fact that you have qemu installed (which I know you already do Alex).
The command looks like this:
qemu-img resize filename [+|-]size[K|M|G|T]
Where filename is the image file, and size is the size you want to enlarge (or shrink) the image.
For example, if you want to extend the image archarm.img by 2GB you would execute:
qemu-img resize archarm.img +2G
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Refering to manpage, Before using this command to shrink a disk image, you MUST use file system and partitioning tools inside the VM to reduce allocated file systems and partition sizes accordingly. Failure to do so will result in data loss!– AntonioKOct 10, 2015 at 14:24