d42f80c65e
* Add Data disk picture to documentation Co-authored-by: Joakim Sørensen <joasoe@gmail.com>
66 lines
2.7 KiB
Markdown
66 lines
2.7 KiB
Markdown
# Partition
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The partition layout is a bit different than the typical setup. We prefer GPT, if possible. With SoCs which don't support GPT, we use a hybrid GPT. For more details about this topic, please refer to the [development](development.md) documentation.
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The system is designed to have as few write operations to the storage media as possible. This means that we only write during the OTA updates and 5-6 times per week on the overlay partition. The data partition receives the main I/O operations and for this reason is ideal for placing on a different drive.
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A visual representation looks like this:
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```text
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-------------------------
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| Bootloader |
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-------------------------
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| Kernel A |
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-------------------------
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| System A |
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-------------------------
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| Kernel B |
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-------------------------
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| System B |
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-------------------------
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| Bootstate |
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-------------------------
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| Overlay |
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...
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-------------------------
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| Data |
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-------------------------
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```
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Sometime the bootloader part can look different because there can be firmware or SPLs for boot the CPU on the SoC.
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## Data disk
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The data partition is the only partition with real I/O. It will be expanded automatically at boot to the full size of the disk.
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## Using datactl to move the data partition.
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In a Home Assistant OS installation, the data is stored on the `/mnt/data` partition of the SD card. This is the only read+write partition on the SD drive. Using the `datactl` move command, this partition can be moved off of the SD card onto an externally connected drive, leaving the rest of the read-only system on the SD.
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The storage capacity of the external drive must be larger than the storage capacity of the existing SD card.
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The command needs to be run from the host console by either connecting a keyboard and monitor or making use of the [debug ssh access](https://developers.home-assistant.io/docs/operating-system/debugging/) over port 22222. The command will not work from within an SSH add-on container.
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Log in as `root` to get to the Home Assistant CLI and then enter `login` to continue to the host.
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Confirm your USB SSD/HD is connected and recognized using `fdisk -l`.
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With the drive connected, use the following command (replacing sdx with your drive, without a partition number):
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```sh
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$ datactl move /dev/sdx
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```
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Enter "yes" to confirm the operation. This will prepare the disk, however, the
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actual move will be running on next reboot. Once complete, the external drive
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will contain the data and will need to be plugged in to successfully boot Home
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Assistant OS.
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