[SOLVED] Error when trying to upgrade

D

darodriguez

Member
Dec 3, 2021
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0
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Misiones, Argentina
informatica.unau.edu.ar
Hi there,

Since we still have PVE 6.4 we want/need to update it. However, we are facing a particular drawback.

The host hosts 25 virtual machines / containers and, when they are running, it is possible to do - for example - an apt-update without problems.
The problem arises when they are shut down, that apt command is no longer responding.

Bash: 
Temporary failure resolving 'download.proxmox.com'

DNS are well known
Bash: 
# cat /etc/resolv.conf
nameserver 8.8.8.8
nameserver 1.1.1.1
nameserver 208.67.222.222

Ping to the gateway works. Also to DNSs

Bash: 
# ping 192.168.10.1
PING 192.168.10.1 (192.168.10.1) 56(84) bytes of data.
64 bytes from 192.168.10.1: icmp_seq=1 ttl=64 time=1.25 ms
64 bytes from 192.168.10.1: icmp_seq=2 ttl=64 time=1.48 ms
64 bytes from 192.168.10.1: icmp_seq=3 ttl=64 time=0.987 ms

Bash: 
# cat /etc/network/interfaces
auto lo
iface lo inet loopback

iface eno99 inet manual

auto vmbr0
iface vmbr0 inet static
    address 192.168.8.2/22
    hwaddress bc:97:e1:9b:76:08
    gateway 192.168.10.1
    bridge-ports eno99
    bridge-stp off
    bridge-fd 0

Routing table
Bash: 
# ip route show
default via 192.168.10.1 dev vmbr0 onlink 
192.168.8.0/22 dev vmbr0 proto kernel scope link src 192.168.8.2

So, any idea that will allow us to achieve the above mentioned goal will be very much appreciated.
 
Hi, darodriguez

dig download.proxmox.com @8.8.8.8

If it times out, the first thing to check is your firewall. If it works here but apt update still shows “Temporary failure resolving,” you need to verify which DNS server apt is actually using (sometimes apt relies on systemd-resolved rather than directly on /etc/resolv.conf).

journalctl -u systemd-resolved

Ideas (the main cause maybe): when guests (VMs/containers) are powered off, the host loses its ability to resolve DNS. In 99% of cases, either the DNS traffic is being blocked by the firewall, or the host is actually doing DNS resolution through one of the containers rather than using the global DNS servers.
 
darodriguez said:
Code: 
# cat /etc/resolv.conf
nameserver 8.8.8.8
nameserver 1.1.1.1
nameserver 208.67.222.222
Click to expand...
Edit that file & add on the first line:
search local

So completely it should read:

Code: 
# cat /etc/resolv.conf
search local
nameserver 8.8.8.8
nameserver 1.1.1.1
nameserver 208.67.222.222
 
GoXLd said:
Hi, darodriguez

dig download.proxmox.com @8.8.8.8

If it times out, the first thing to check is your firewall. If it works here but apt update still shows “Temporary failure resolving,” you need to verify which DNS server apt is actually using (sometimes apt relies on systemd-resolved rather than directly on /etc/resolv.conf).

journalctl -u systemd-resolved

Ideas (the main cause maybe): when guests (VMs/containers) are powered off, the host loses its ability to resolve DNS. In 99% of cases, either the DNS traffic is being blocked by the firewall, or the host is actually doing DNS resolution through one of the containers rather than using the global DNS servers.
Click to expand...
The latter is the case, but I can't find any file referencing / pointing to the IP of the host where the DNS runs.
 
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