kernel: enable CONFIG_OVERLAY_FS_METACOPY for sysbox#38
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Without metacopy, sysbox's chown-based UID remapping copies full file contents on overlayfs, which is extremely slow for large container images. With metacopy enabled, overlayfs copies only metadata during chown operations.
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Summary
CONFIG_OVERLAY_FS_METACOPY=yin the sysbox kernel config fragment--disable-ovfs-on-idmapped-mounttosysbox-mgr.serviceBackground
We are no longer pursuing the overlayfs
FS_ALLOW_IDMAPkernel patch route.Current upstream overlayfs still does not support that path, so sysbox must avoid trying to use overlayfs on idmapped mounts. With
--disable-ovfs-on-idmapped-mount, sysbox consistently uses its compatibility fallback instead of hitting the broken path.That fallback is only practical if overlayfs metacopy is enabled. Without
CONFIG_OVERLAY_FS_METACOPY=y, sysbox's chown-based UID remapping can trigger full data copies on large images and become prohibitively slow. With metacopy enabled, only metadata is copied, which keeps container startup usable.Test plan
bitbake virtual/kernelCONFIG_OVERLAY_FS_METACOPY=yin kernel configsysbox-mgrstarts with--disable-ovfs-on-idmapped-mount