Score:1

Ubuntu

Webcam works as root but not as normal user: what permissions do I need to change?

Daniel Hatton

6/6/24, 2:14 PM

When I run cheeseas root, I can see the video stream from my webcam just fine. However, when I run it as a normal user, I get "No device found". The normal user in question is in a group (video) that has read and write permission on the relevant device file /dev/video0. How do I get webcam access as a normal user, please?

Output from cheese run as root is:

(cheese:5512): GLib-GObject-CRITICAL **: 14:43:01.263:
g_value_dup_string: assertion 'G_VALUE_HOLDS_STRING (value)' failed
(cheese:5512): GLib-GObject-CRITICAL **: 14:43:03.915:
g_value_dup_string: assertion 'G_VALUE_HOLDS_STRING (value)' failed
root@verderer:~# cheese
(cheese:5786): GLib-GObject-CRITICAL **: 14:58:42.863:
g_value_dup_string: assertion 'G_VALUE_HOLDS_STRING (value)' failed
(cheese:5786): GLib-GObject-CRITICAL **: 14:58:45.498:
g_value_dup_string: assertion 'G_VALUE_HOLDS_STRING (value)' failed

Output from cheese run as normal user is:

(cheese:5650): Gdk-WARNING **: 14:47:18.091: Native Windows taller
than 65535 pixels are not supported
** Message: 14:47:18.151: cheese-application.vala:222: Error during camera setup: No device found
(cheese:5650): cheese-CRITICAL **: 14:47:18.185:
cheese_camera_device_get_name: assertion 'CHEESE_IS_CAMERA_DEVICE
(device)' failed
(cheese:5650): GLib-CRITICAL **: 14:47:18.185: g_variant_new_string:
assertion 'string != NULL' failed
(cheese:5650): GLib-CRITICAL **: 14:47:18.185: g_variant_ref_sink:
assertion 'value != NULL' failed
(cheese:5650): GLib-GIO-CRITICAL **: 14:47:18.185:
g_settings_schema_key_type_check: assertion 'value != NULL' failed
(cheese:5650): GLib-CRITICAL **: 14:47:18.185:
g_variant_get_type_string: assertion 'value != NULL' failed
(cheese:5650): GLib-GIO-CRITICAL **: 14:47:18.185:
> g_settings_set_value: key 'camera' in 'org.gnome.Cheese' expects type's', but a GVariant of type '(null)' was given
(cheese:5650): GLib-CRITICAL **: 14:47:18.185: g_variant_unref:
assertion 'value != NULL' failed
** (cheese:5650): CRITICAL **: 14:47:18.185: cheese_preferences_dialog_setup_resolutions_for_device: assertion
'device != NULL' failed

200

1 + 3

permissions

webcam

Daniel Hatton

6/6/24, 6:09 PM

Would the downvoter care to provide reasoning? Have I missed an easily-Googlable solution again?

Daniel Hatton

6/6/24, 6:23 PM

Potentially relevant extra datum: linphone run as the same normal user _does_ detect that a camera is present; when I click linphone's "video preview" button, linphone manages to turn on a green LED on the camera, but then crashes and coredumps, with no image ever shown.

Daniel Hatton

6/7/24, 11:15 AM

More data: uvccapture run as the same normal user fails to capture an image, with the error message "ioctl querycontrol error 22"; however, guvcview run as the same normal user can successfully display, record, and capture stills from the video stream (although even guvcview repeatedly complains about "V4L2_CORE: (UVCIOC_CTRL_MAP) Error: Inappropriate ioctl for device").

Score:-3

Ubuntu

waltinator

6/6/24, 9:44 PM

Look at the ownership and permissions of your camera: ls -l /dev/video*. Notice that it allows rw access to members of the video group.

Add yourself to the video group, with this command:

sudo adduser $USER video

Then fully logout and login. Group membership is applied by login (and the newgrp command).

+ 5

Daniel Hatton

6/7/24, 8:57 AM

Already done that. I thought I mentioned that n the question, didn't I?

waltinator

6/7/24, 5:04 PM

Already done what? [Edit] your Question and show us (as "normal user ") `id;ls -l /dev/video*` on your system.

Daniel Hatton

6/7/24, 5:56 PM

Already added the relevant normal user to group "video" and logged out and back in. Output of the command you suggest is uid=1000(dan) gid=1000(dan) groups=1000(dan),4(adm),24(cdrom),27(sudo),30(dip),44(video),46(plugdev),110(render),122(lpadmin),135(lxd),136(sambashare),138(docker),1002(compilers) crw-rw----+ 1 root video 81, 0 Jun 7 10:59 /dev/video0

waltinator

6/7/24, 10:39 PM

Comments are designed for US to ask YOU questions about your Question. You should [Edit] your question to add information. By updating your Question, and using the formatting buttons, you make all the information available to new readers. People shouldn't have to read a long series of comments to get the whole story. AskUbuntu is a Question and Answer site, not a conversation site. If you have an update, [edit] your Question. If you have a new question, see [Ask].

Daniel Hatton

6/8/24, 8:40 AM

The information is already in the question.

Elon Musk

I sit in a Tesla and translated this thread with Ai:

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