62 lines
2.1 KiB
Markdown
62 lines
2.1 KiB
Markdown
# image files
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- [image files](#image-files)
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- [create image file](#create-image-file)
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- [resize image](#resize-image)
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- [resize partition](#resize-partition)
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- [mount image files](#mount-image-files)
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- [setup image for Raspberry PI](#setup-image-for-raspberry-pi)
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## create image file
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To create an image file, use:
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```bash
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dd if=/dev/zero of=<image-file> bs=<block-size> count=<count>
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# example: generate image with size of exactly 7.8 Gb
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dd if=/dev/zero of=test.img bs=1000000 count=7800 conv=fsync
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```
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## resize image
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One can change an images size with `truncate --size=<size> <image-file>`.
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This is usually used to increase image size in order to increase the file system size (i.e. make more space for rootfs).
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If the goal is to decrease the memory footprint, extra care has to be taken to not cripple the filesystem.
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## resize partition
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One can resize a partition (if there is no data afterwards) by deleting and remaking it with `fdisk`. Make sure to choose the same start sector!.
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## mount image files
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To mount an image file use:
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```bash
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mount -o loop <path/to/image-file> <mount-point>
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```
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If the image contains multiple partitions one needs to setup a loop device first:
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```bash
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losetup --find --show <path/to/image-file> -P
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# can be shortened to:
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losetup -f <path/to/image-file> -P
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```
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Afterwards the partitions of the image should be shown as loopXpY and can be mounted like any other device.
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## setup image for Raspberry PI
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This is a quick step through the setup of a raspbian image:
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1. download image
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1. truncate image (see [resize image](#resize-image))
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1. resize partition with fdisk (see [resize partition](#resize-partition))
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1. setup loop device for image (see [mount image files](#mount-image-files))
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1. resize filesystem on said partition (loop device) with `resize2fs` (or similar)
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1. mount boot partition (see [mount image files](#mount-image-files))
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1. add empty file `ssh` to boot partition
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1. add userconf.txt to boot partition, to set up initial user & password
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1. disable resize script in boot/cmdline.txt (something with `firstboot` or `resize`)
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1. unmount partition and detach loop device
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