[Help] I have encountered some problems when using Debian, so I will ask you for help if GOOGLE doesn't exist!

[Help] I have encountered some problems when using Debian, so I will ask you for help if GOOGLE doesn't exist! -- Debian information of the Linux release-the following is a detailed description. Hello everyone, I have encountered some problems while using Debian, but GOOGLE cannot find them. So I 'd like to ask you for advice! Thank you!

Question 1.
After logging in with the root user, even if the program is VIM, a prompt is displayed:
Xlib: connection to ": 0.0" refused by server
Xlib: No protocol specified

After xvidtune is executed, the following message is displayed:
Xlib: connection to ": 0.0" refused by server
Xlib: No protocol specified

Error: Can t open display: 0.0

Question 2.
When Virtualbox is used, the following message is displayed after NAT is selected:

A Domain Name Server (DNS) for NAT networking cocould not be determined. please check your/etc/resolv. conf for nameserver entries. either add one manually (man resolv. conf) or ensure that your host is correctly connected to an ISP. if you ignore this warning the guest will not be able to perform nameserver lookups and it will probably observe delays if trying so.


Error ID: NoDNSforNAT
Severe: Warning

Check/etc/resolv. conf. There is only one line of comment in it. It seems that you don't want to modify it. I didn't dare to change it when I saw this prompt ~!

Question 3.
How can I set Virtualbox to connect to the host? When I set the IP address for internat, the host cannot be pinged ....


I hope you can help me with your answers. Thank you to all your friends! Thank you!





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