GNOME桌面通过命令行修改壁纸失败的问题排查求助

大家好，我现在在一个学习项目里遇到了问题，按照要求需要从命令行下载指定图片并设置为GNOME桌面壁纸，但操作后完全没效果，感觉这像是个测试，但我搞不懂为什么步骤里把图片下载到~/Downloads目录，却让我设置/tmp路径的图片？

给定的操作步骤 #

要求先下载图片，再用命令设置壁纸：

$ wget -O ~/Downloads/wallpaper.jpg  "https://raw.githubusercontent.com/hoppersroppers/hoppersroppers.github.io/main/_layouts/constitution.jpg"
$ gsettings set org.gnome.desktop.background picture-uri file:////tmp/wallpaper.jpg

预期背景会变成一艘船的图片，但实际完全没变化，我尝试了各种排查操作，以下是我的命令行记录：

我的操作及输出 #

ob@adminbaby:~/Desktop$  wmctrl -m
Name: GNOME Shell
Class: N/A
PID: N/A
Window manager's "showing the desktop" mode: OFF

bob@adminbaby:~/Desktop$  gsettings set org.gnome.desktop.background picture-uri file:////tmp/wallpaper.jpg

bob@adminbaby:~/Desktop$ pwd
/home/bob/Desktop

bob@adminbaby:~/Desktop$ ls
first

bob@adminbaby:~/Desktop$ sudo  gsettings set org.gnome.desktop.background picture-uri file:////tmp/wallpaper.jpg
[sudo] password for bob:
(process:2230): dconf-WARNING **: 16:39:33.016: failed to commit changes to dconf: Failed to execute child process “dbus-launch” (No such file or directory)

bob@adminbaby:~/Desktop$  gsettings set org.gnome.desktop.background picture-uri file://// ~/Downloads/wallpaper.jpg
Usage:
gsettings [--schemadir SCHEMADIR] set SCHEMA[:PATH] KEY VALUE
Set the value of KEY to VALUE

Arguments:
SCHEMADIR A directory to search for additional schemas
SCHEMA    The name of the schema
PATH      The path, for relocatable schemas
KEY       The key within the schema
VALUE     The value to set

bob@adminbaby:~/Desktop$ sudo  gsettings set org.gnome.desktop.background picture-uri file:////home/bob/Downloads.jpg
(process:2240): dconf-WARNING **: 16:40:57.446: failed to commit changes to dconf: Failed to execute child process “dbus-launch” (No such file or directory)

bob@adminbaby:~/Desktop$  gsettings set org.gnome.desktop.background picture-uri file:////home/bob/Downloads/wallpaper.jpg

bob@adminbaby:~/Desktop$ sudo  gsettings set org.gnome.desktop.background picture-uri file:////tmp/wallpaper.jpg

bob@adminbaby:~/Desktop$  wmctrl -m
Command 'wmctrl' not found, but can be installed with:
sudo apt install wmctrl

bob@adminbaby:~/Desktop$ sudo apt install wmctrl
Reading package lists... Done
Building dependency tree... Done
Reading state information... Done
The following NEW packages will be installed:
wmctrl
0 upgraded, 1 newly installed, 0 to remove and 0 not upgraded.
Need to get 20.6 kB of archives.
After this operation, 63.5 kB of additional disk space will be used.
Get:1 http://us.archive.ubuntu.com/ubuntu lunar/universe amd64 wmctrl amd64 1.07-7ubuntu1 [20.6 kB]
Fetched 20.6 kB in 0s (62.8 kB/s)
Selecting previously unselected package wmctrl.
(Reading database ... 203962 files and directories currently installed.)
Preparing to unpack .../wmctrl_1.07-7ubuntu1_amd64.deb ...
Unpacking wmctrl (1.07-7ubuntu1) ...
Setting up wmctrl (1.07-7ubuntu1) ...
Processing triggers for man-db (2.11.2-1) ...

bob@adminbaby:~/Desktop$  wmctrl -m
Name: GNOME Shell
Class: N/A
PID: N/A
Window manager's "showing the desktop" mode: OFF

bob@adminbaby:~/Desktop$ realpath -s wallpaper.jpg
/home/bob/Desktop/wallpaper.jpg

bob@adminbaby:~/Desktop$ sudo  gsettings set org.gnome.desktop.background picture-uri file://///home/bob/Desktop/wallpaper.jpg
(process:2829): dconf-WARNING **: 16:53:30.948: failed to commit changes to dconf: Failed to execute child process “dbus-launch” (No such file or directory)

bob@adminbaby:~/Desktop$ gsettings set org.gnome.desktop.background picture-uri file:///home/bob/Downloads/wallpaper.jpg

bob@adminbaby:~/Desktop$ realpath -s wallpaper.jpg
/home/bob/Desktop/wallpaper.jpg

bob@adminbaby:~/Desktop$ sudo  gsettings set org.gnome.desktop.background picture-uri file://///home/bob/Desktop/wallpaper.jpg
(process:2829): dconf-WARNING **: 16:53:30.948: failed to commit changes to dconf: Failed to execute child process “dbus-launch” (No such file or directory)

我的疑问 #

• 为什么给定的步骤里把图片下载到~/Downloads，却要求设置/tmp/wallpaper.jpg？这明显路径不对应啊？
• 不用sudo执行gsettings命令时没有报错，但壁纸完全没变化；用sudo执行就会出现dbus-launch找不到的错误，这是权限问题吗？
• 我已经通过realpath确认了图片的绝对路径，但设置后还是没效果，有没有大佬能指点下问题出在哪？

备注：内容来源于stack exchange，提问作者bryce colwell