Mender Convert - Data Partition / Rootfs Overlay Permissions

General Discussions
1

Hi,

Following a previous discussion I’ve been looking into using mender convert rather than snapshots

And I think it’s very nearly there however I have two areas I’m not clear on:

I’m running a program which writes out to a file in the users home directory, I’d like this file to persist between rootfs updates.

I understand that the /data partition should be used for this however I don’t have write access as the partition is owned by root.

Is there a way to configure mender-convert to change the permissions on the created partitions during the conversion?

Or would it be possible to use state scripts to move files from home to /data and back again during the update process?

My other issue is using rootfs overlays, is there any information on what the permissions / owner of overlay files need to be on the host machine or how ownership is assigned during conversion?

I can’t seem to reliably recreate the issue but when using an overlay (just adding a file to home directory) the file is added correctly however the permissions of other files seemed to be randomly altered (e.g. /etc is owned by pijuice which is a user created by the UPS software similar for random files in the home directory)

Any assistance of info would be greatly appreciated

Thanks

2

With respects to data partition, in your golden master, setup the /data folder with a subfolder structure as per your requirements with correct permissions and it’ll get copied to the data partition during mender-convert conversion

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3

You also have hooks available to make changes during the mender-convert process

https://docs.mender.io/system-updates-debian-family/convert-a-mender-debian-image/customization

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4

Thank you for the quick reply

Just to clarify, I don’t need a separate data partition on my master image but only a folder called data placed at root /?

5

Yes, that’s correct. Also, regarding ownership, I think anything created in your golden master will be copied into the new image with the same ownership and permissions.

You can also add files through the mender-convert rootfs-overlay in a similar fashion.

Drew

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6

Thanks for the reply

Tried this morning and no luck, do I need to alter a config / parameter somewhere?
I’m just using the base scripts/configs from mender-convert and adding a custom config just for LZMA compression

I’ve added a data folder to my golden image’s root which contains a second folder inside (backup) that is owned by the user so they have a place to backup to between rootfs updates.

However it doesn’t seem to copy over to the converted image/artifact, after uploading and deploying I see /data/mender/... but no /data/backup/... on the updated Pi

7

if starting with the golden master, then you need to do a full re-image of the device from the full disk image created by mender-convert, it wont be part of the mender-artifact as far as i’m aware.

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8

Ah of course, enrolled devices will already have a /data partition configured which isn’t being touched by a rootfs update

Flashed a full image and that Pi seems to have the correct structure with the backup folder under /data will do some testing with it tomorrow

I guess I’ll have to reflash my existing devices or remote in and manually restructure /data

Thanks again