Can mender support going to a smaller SD card footprint?

General Discussions
1

Hi, I’m a total NOOB at mender so bear with me. I just wanted to hear from the experts how to get started on something.

My team have a yocto project using a 16GB sd card today, and we have used mender to do many updates already. I’m joining the project after it’s been shipped for several years. What I don’t know is if we could shift to using smaller SD cards. What are the implications/challenges if we went from a mender that uses MENDER_STORAGE_TOTAL_SIZE_MB = “14784” to one that would fit in say a 4GB or 8GB card? I also see that we have MENDER_DATA_PART_SIZE_MB = “4096”.

Any recommendations on where to start, and if this is going to be a small/medium/large/huge effort?

2

Our standard demo is only slightly over 600M. Mender doesn’t have high requirements here as long as the dual rootfs is satisfied, and there is a tiny bit of space available for the data partition. It depends entirely on what you have in your storage to begin with. Unless you have a large application in your rootfs, or large storage requirements on the data partition, I would anticipate quite low effort to reduce the size.

3

Ok, thanks. Just to clarify, you’re saying that if we change mender to work with smaller sizes for these defined areas I mentioned, then upgrading already deployed devices with these old values (i.e. 14GB for mender data partition or 4GB for data part size) to a new yocto build shouldn’t be very hard as long as the final yocto build only requires the new sizes we pick?

So if we’re only using say 1GB of user persist data, then we could shrink the 4GB data part size, to 1.5GB and mender upgrade will take care of things?

4

Mender does not modify the partition sizes on already deployed devices. Meaning that if you have devices out in the field that have a 4GB data part size, that will remain unchanged on those devices.

Any changes you make right now will only affect “new devices” that you provision with that configuration. And since you are going from bigger to smaller sizes that should not be a problem, because the Mender Artifact (possibly ext4 payload) size will be smaller and should fit on the devices that had the following definition,

MENDER_STORAGE_TOTAL_SIZE_MB = “14784”
MENDER_DATA_PART_SIZE_MB = “4096”

What you will not be able to do is to deploy “older” Mender Artifacts that where created using above configuration to the new configuration.