How to fix ssh: Could not resolve hostname github.com: Name or service not known in Git

First, verify that your network connection is working at all:

# Test if you can reach the internet (IP-based, no DNS needed)
ping -c 4 8.8.8.8

If this fails, you have a network connectivity issue, not just a DNS problem. Check:
- Is your WiFi/ethernet connected?
- Is your VPN connected (if required)?
- Are network cables properly plugged in?

If ping to 8.8.8.8 works, then the problem is specifically DNS resolution.

Check if DNS is working for any domain:

# Try to resolve github.com using system DNS
host github.com

# Or using nslookup
nslookup github.com

# Or using dig
dig github.com

If these fail, try using a specific DNS server to isolate the problem:

# Test with Google's DNS
host github.com 8.8.8.8

# Or with Cloudflare's DNS
nslookup github.com 1.1.1.1

If the second set of commands works but the first doesn't, your system's DNS configuration needs to be fixed.

Check and update your DNS resolver configuration:

# View current DNS configuration
cat /etc/resolv.conf

If it's empty or has incorrect entries, add public DNS servers:

# Edit resolv.conf (may need sudo)
sudo nano /etc/resolv.conf

Add these lines:

nameserver 8.8.8.8
nameserver 8.8.4.4
nameserver 1.1.1.1

Save and test:

ping github.com

Note: On systems using systemd-resolved or NetworkManager, changes to /etc/resolv.conf may be overwritten. See the next step for a permanent fix.

WSL often auto-generates /etc/resolv.conf with incorrect settings. To fix this permanently:

Step 1: Prevent auto-generation of resolv.conf

sudo nano /etc/wsl.conf

Add these lines:

[network]
generateResolvConf = false

Step 2: Remove the auto-generated symlink and create a proper resolv.conf

# Remove the symlink
sudo rm /etc/resolv.conf

# Create a new resolv.conf with public DNS
sudo bash -c 'echo "nameserver 8.8.8.8" > /etc/resolv.conf'
sudo bash -c 'echo "nameserver 1.1.1.1" >> /etc/resolv.conf'

Step 3: Restart WSL

In Windows PowerShell (as Administrator):

wsl --shutdown

Then reopen your WSL terminal and test:

ping github.com

Sometimes IPv6 DNS or connectivity issues cause this error. You can force SSH to use IPv4:

Option 1: One-time fix via command line

git clone -c core.sshCommand="ssh -4" [email protected]:user/repo.git

Option 2: Configure SSH to always use IPv4 for GitHub

Edit or create ~/.ssh/config:

nano ~/.ssh/config

Add:

Host github.com
    AddressFamily inet
    Hostname github.com
    User git
    IdentityFile ~/.ssh/id_ed25519

Host *.github.com
    AddressFamily inet

Option 3: Set globally in Git config

git config --global core.sshCommand "ssh -4"

Sometimes the DNS resolver service just needs a restart:

On Ubuntu/Debian with systemd-resolved:

sudo systemctl restart systemd-resolved

On systems with NetworkManager:

sudo systemctl restart NetworkManager
# or
sudo service network-manager restart

On older systems:

sudo service networking restart

Flush DNS cache (if using systemd-resolved):

sudo systemd-resolve --flush-caches
# or on newer systems
sudo resolvectl flush-caches

Firewalls or corporate proxies might be blocking DNS queries:

Check if DNS port is blocked:

# Try connecting to DNS server on port 53
nc -zv 8.8.8.8 53

If behind a corporate proxy, you may need to:

1. Use your company's internal DNS servers instead of public ones
2. Configure Git to use HTTPS instead of SSH:

# Change remote from SSH to HTTPS
git remote set-url origin https://github.com/user/repo.git

# For authentication, set up credential caching
git config --global credential.helper cache

Check proxy settings:

echo $http_proxy
echo $https_proxy
echo $no_proxy

If proxies are set, you might need to configure Git to use them:

git config --global http.proxy http://proxy.company.com:8080
git config --global https.proxy http://proxy.company.com:8080

If SSH continues to have DNS issues, switching to HTTPS is a reliable alternative:

Change an existing remote:

# View current remote
git remote -v

# Change from SSH to HTTPS
git remote set-url origin https://github.com/username/repository.git

Clone new repos using HTTPS:

# Instead of:
# git clone [email protected]:user/repo.git

# Use:
git clone https://github.com/user/repo.git

Set up credential storage for HTTPS:

# Cache credentials for 1 hour
git config --global credential.helper 'cache --timeout=3600'

# Or store permanently (less secure)
git config --global credential.helper store

# On macOS, use Keychain
git config --global credential.helper osxkeychain

# On Windows, use Windows Credential Manager
git config --global credential.helper wincred

For GitHub, you can also use a Personal Access Token (PAT) instead of password authentication.

If DNS is completely broken and you need an immediate workaround, you can manually add GitHub's IP:

Get GitHub's current IP addresses:

# From a machine where DNS works, or check GitHub's docs
dig github.com +short

Add to /etc/hosts:

sudo nano /etc/hosts

Add a line like:

140.82.121.4 github.com

Important warnings:
- This is a temporary workaround, not a permanent fix
- GitHub's IP addresses can change
- This won't work for GitHub subdomains (like raw.githubusercontent.com)
- Fix your actual DNS configuration as soon as possible

To remove later:

sudo nano /etc/hosts
# Remove the github.com line you added