epkowa recognizes GT-F720 USB scanner only as root

[royneary]

After upgrading to 20.03 my scanner Epson Perfection V30 was not recognized anymore. Since #82909 has been applied, it's recognized as root, but not as unprivileged user. My user is in the groups scanner and lp as suggested in https://nixos.wiki/wiki/Scanners.

lsusb shows:

Bus 001 Device 002: ID 04b8:0131 Seiko Epson Corp. GT-F720 [GT-S620/Perfection V30/V300 Photo]

To Reproduce
Steps to reproduce the behavior:

$ scanimage -L
$

Expected behavior
scanimage -L should list my scanner as it did on 19.09.

Additional context
sudo SANE_DEBUG_SANEI_USB=3 scanimage -L shows

[sanei_usb] sanei_usb_find_devices: vendor=0x04b8, product=0x0131

but without sudo it doesn't.

sudo SANE_DEBUG_DLL=3 scanimage -L shows this:

[dll] add_backend: adding backend `epkowa'
[dll] sane_get_devices
[dll] load: searching backend `epkowa' in `/nix/store/kyyjfjx4i2vgldbxjn7z6nkr1dxb7c05-sane-config/lib/sane:/nix/store/sdqv2is6wi2ycr8ahpb5ww9zlf9f7k4j-sane-backends-1.0.28/lib/sane'
[dll] load: dlopen()ing `/nix/store/kyyjfjx4i2vgldbxjn7z6nkr1dxb7c05-sane-config/lib/sane/libsane-epkowa.so.1'
[dll] init: initializing backend `epkowa'

whereas without sudo it shows:

[dll] add_backend: adding backend `epkowa'
[dll] sane_get_devices
[dll] load: searching backend `epkowa' in `/nix/store/sdqv2is6wi2ycr8ahpb5ww9zlf9f7k4j-sane-backends-1.0.28/lib/sane'
[dll] load: couldn't find backend `epkowa' (No such file or directory)

Notify maintainers
@symphorien @dominikh

Metadata

• system: "x86_64-linux"
• host os: Linux 5.4.45, NixOS, 20.03.2133.8946799e079 (Markhor)
• multi-user?: yes
• sandbox: yes
• version: nix-env (Nix) 2.3.6
• channels(root): "nixos-20.03.2133.8946799e079"
• nixpkgs: /nix/var/nix/profiles/per-user/root/channels/nixos

Maintainer information:

# a list of nixpkgs attributes affected by the problem
attribute: epkowa
# a list of nixos modules affected by the problem
module: sane

[royneary]

I found out that as root LD_LIBRARY_PATH is set to /nix/store/kyyjfjx4i2vgldbxjn7z6nkr1dxb7c05-sane-config/lib/sane, wheras for my unprivileged user it's empty.

If I set LD_LIBRARY_PATH, I can scan.

$ export LD_LIBRARY_PATH=/nix/store/kyyjfjx4i2vgldbxjn7z6nkr1dxb7c05-sane-config/lib/sane
$ scanimage -L
device `epkowa:interpreter:001:002' is a Epson Perfection V30 flatbed scanner

Why is LD_LIBRARY_PATH not set for my user?

[symphorien]

This variable is normally set by /etc/profile. Could it be that you are using an unusual shell that does not source /etc/profile ?

[royneary]

I'm using bash and AFAIK I didn't configure anything special for it.

What I find strange is that SANE_CONFIG_DIR is set:

$ echo $SANE_CONFIG_DIR
/nix/store/kyyjfjx4i2vgldbxjn7z6nkr1dxb7c05-sane-config/etc/sane.d

I had a look in /etc/profile and both SANE_CONFIG_DIR and LD_LIBRARY_PATH are set from /nix/store/1iwzrq3w7g3r9dsddcmzzpki5piyvsfm-set-environment. So LD_LIBRARY_PATH seems to be overwritten after sourcing /etc/profile.

[royneary]

It seems to be Gnome's fault. When I login on a non-graphical shell, LD_LIBRARY_PATH is set correctly.

[royneary]

closing in favour of #90201