DNS resolution fails in LXC containers, but only for apt.

[elderx]

When create LXC container from default Ubuntu 22.04 template i can not run apt udate inside the LXC container since apt cannot resolve any DNS names. Pinging domains works, running dig works for domains that apt is trying. Only thing that is not working, is that apt can not resolve DNS names. I have found multiple people complaining same thing, but so far 0 resolved.

 

[LnxBil]

Please post the actual commands and results. Just stating that it does not work is not enough.

 

[elderx]

I figured i was since i had these in proxmox
# post-up iptables -t nat -A PREROUTING -p tcp --dport 80 -j DNAT --to-destination 10.0.0.101
# post-up iptables -t nat -A PREROUTING -p tcp --dport 443 -j DNAT --to-destination 10.0.0.101

I was thinking of running an Nginx reverse proxy and i wanted to forward ports 80 and 443 to the LXC container running the Nginx. Then the Nginx will proxypass to other containers running different services and i was able to map my own domains subdomains to those containers running services and access the them through the Nginx reverse proxy. Everything was working except that i could not run apt from inside those LXC containers. In the above that 10.0.0.101 is the ip of Nginx reverse proxy LXC container.

Any suggestions how to implement that in a way that apt can still resolve dns ?

 

[LnxBil]

Those iptables rules are too broad. Use -d <destination ip> in order to not fuck up everything.