You're quicker than expected, thanks for answering.

Not sure how to check if lz4 was builtin, but considering that erofsfuse is only about 34.5KB (stripped) I would guess not?

Here's the output of erofsfuse -d (it prints this but never exists back to shell unless I do Ctrl+C):

erofsfuse 1.3
disk: product.img
mountpoint: product-mnt
dbglevel: 7
FUSE library version: 2.9.9
nullpath_ok: 0
nopath: 0
utime_omit_ok: 0
unique: 1, opcode: INIT (26), nodeid: 0, insize: 56, pid: 0
INIT: 7.27
flags=0x003ffffb
max_readahead=0x00020000
EROFS: erofsfuse_init() Line[23] Using FUSE protocol 7.27
INIT: 7.19
flags=0x00000011
max_readahead=0x00020000
max_write=0x00020000
max_background=0
congestion_threshold=0
unique: 1, success, outsize: 40

On Fri, 20 Aug 2021 at 15:49, Gao Xiang <xiang@kernel.org> wrote:

Hi Igor,

On Fri, Aug 20, 2021 at 03:34:05PM +0300, Igor Eisberg wrote:
> Hey there, getting straight to the point.
> Our team is using Debian 10, in which erofs mounting is not supported and
> we have no option of updating the kernel, nor do we have sudo permissions
> on this server.
>
> Our only choice is to use erofsfuse to mount an Android image (compression
> was used on that image), for the sole purpose of extracting its contents to
> another folder for processing.
> Tried on Debian 10, pop_OS! and even the latest Kubuntu (where native
> mounting is supported), but on all of them I could not copy files which are
> compressed from the mounted image to another location (ext4 file system).
>
> The error I'm getting is: "Operation not supported (95)"
>

Thanks for your feedback.

Could you check if lz4 was built-in when building erofsfuse? I guess
that is the reason (lack of lz4 support builtin).

If not, could you add -d to erofsfuse when starting up?

Thanks,
Gao Xiang

> Notes:
> * Only extremely small (< 1 KB) files which are stored uncompressed are
> copied successfully.
> * Copying works perfectly when mounting the image with "sudo mount" on the
> latest Kubuntu, so it has to be something with erofsfuse.
>
> Anything you can do to help resolve this?
>
> Best,
> Igor.