question: sometimes, for ext4 partition, no sparse compression is done about fwup HOT 4 CLOSED

Hi Tom,

The sparse file feature is depends on what filesystem that you're using on the build server. The way it works is that fwup asks the OS where the holes in a file are and then saves that info to the archive.

About a year ago, I started seeing some CI servers that have filesystems which were pretty unreliable with reporting the holes in sparse files. I never investigated since all of my work since then has been with compressed filesystems that didn't need the feature. I "think" that the common thread was that if the CI server was a virtual machine or a dedicated machine, it worked and if it was in a Docker container, it didn't. I'm not sure, though, and that doesn't make sense to me. My first guess would be to see what filesystem is in use on your build server and see if that provides a hint.

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Hello,

Thanks for the reply. It seems somehow, the file is not sparse, and it's on a pure ext4 filesystem. I am using yocto, and it seems on my buildserver, I have the file with a timestamp, and one without the timestamp. I discovered a tool called fallocate, which is on linux, and you can recreate a file to be sparse. So I tried with "fallocate -d rootfs.img -v" on the rootfs.img with a timestamp, and it only detected 32mb of sparse space. And I tried with the non-timestamped version, and that could detect 400 mb of sparse space. When I now run fwup using the non-timestamped version, then fwup detects correctly that it is a sparse file and the fwup data directory contains the 1,2 GB file instead of a 1,6 GB file.
So that hopefully fixes it for me now 🤞

from fwup.

Hi, it seems that fixed it for me.

from fwup.

Interesting. Thanks for following up.

from fwup.