How to fix W: Failed to fetch URL Temporary failure resolving 'hostname' in APT

APTINTERMEDIATEHIGH

This error occurs when apt cannot resolve the domain name for package repositories due to DNS configuration issues or network connectivity problems. Common causes include missing DNS servers, network interface misconfiguration, or systemd-resolved service issues.

What this error means

When apt attempts to fetch packages from repositories, it needs to resolve the repository's hostname (e.g., archive.ubuntu.com) to an IP address. This error means the system's DNS resolver cannot translate the hostname into an IP address. This is typically a network configuration issue rather than a problem with apt itself. The error can occur during 'apt update' or when installing packages.

How to fix "W: Failed to fetch URL Temporary failure resolving 'hostname'"

1Verify internet connectivity first

Before troubleshooting DNS, confirm your network connection is working:

bash

# Ping Google's public DNS server
ping -c 4 8.8.8.8

If this fails, your system has no internet connection. Check your network cable, WiFi, or contact your ISP.

If the ping succeeds but apt still fails, you have a DNS-specific issue.

2Check current DNS configuration

View what DNS servers your system is currently configured to use:

bash

cat /etc/resolv.conf

You should see at least one nameserver line. If the file is empty or missing, that's your problem.

On newer Ubuntu/Debian systems (18.04+), DNS is managed by systemd-resolved. Check its status:

bash

sudo systemctl status systemd-resolved

You should see active (running) in the output.

3Add DNS servers manually (temporary fix)

As a quick fix, add Google's public DNS servers:

bash

sudo tee /etc/resolv.conf > /dev/null << EOF
nameserver 8.8.8.8
nameserver 8.8.4.4
EOF

Then test:

bash

apt update

Note: This change may not persist after reboot if systemd-resolved rewrites the file.

4Configure DNS permanently (systemd-resolved)

For Ubuntu 18.04+ systems using systemd-resolved, edit the resolver configuration:

bash

sudo nano /etc/systemd/resolved.conf

Uncomment or add these lines:

ini

[Resolve]
DNS=8.8.8.8 8.8.4.4
FallbackDNS=1.1.1.1 1.0.0.1

Save the file (Ctrl+X, then Y, then Enter).

Restart the service:

bash

sudo systemctl restart systemd-resolved

Verify the fix:

bash

systemd-resolve --status
apt update

5Configure DNS permanently (older systems)

On systems using NetworkManager or older Debian/Ubuntu versions:

bash

sudo nano /etc/resolv.conf

Add Google's DNS servers:

bash

nameserver 8.8.8.8
nameserver 8.8.4.4

Make the file immutable to prevent it from being overwritten:

bash

sudo chattr +i /etc/resolv.conf

To later undo this: sudo chattr -i /etc/resolv.conf

6Test DNS resolution

Verify that DNS is now working:

bash

# Test DNS resolution
nslookup archive.ubuntu.com

# Or use host command
host archive.ubuntu.com

# Or use dig
dig archive.ubuntu.com

You should see the IP address in the output. If this succeeds, apt should now work:

bash

sudo apt update
sudo apt install -y <package-name>

7Fix DNS in Docker containers

If this error occurs inside a Docker container, configure Docker's DNS settings.

Temporary fix (for one container):

bash

docker run --dns 8.8.8.8 --dns 8.8.4.4 <image-name>

Permanent fix (edit Docker daemon config):

bash

sudo nano /etc/docker/daemon.json

Add or modify:

json

{
  "dns": ["8.8.8.8", "8.8.4.4"]
}

Restart Docker:

bash

sudo systemctl restart docker

How to fix W: Failed to fetch URL Temporary failure resolving 'hostname' in APT

What this error means

Typical symptoms

Common causes

How to fix "W: Failed to fetch URL Temporary failure resolving 'hostname'"

Advanced notes

Related errors

Official resources & further reading