In Ubuntu 10.04 (Lucid Lynx), the /etc/hostname file should typically contain only the short hostname of the system, not the fully-qualified domain name (FQDN). This follows the traditional Unix convention where the hostname file stores just the machine's name.

The distinction between these is important:

# Correct (short hostname):
webserver

# Incorrect (FQDN):
webserver.example.com

The FQDN should be properly configured in these files:

• /etc/hosts - Should contain entries mapping IPs to both short and FQDN
• DNS configuration - Should have proper forward and reverse records

Example /etc/hosts entry:

127.0.0.1   localhost
192.168.1.10 webserver.example.com webserver

To check and modify the hostname:

# View current hostname
hostname
hostname -f  # shows FQDN

# Temporarily change hostname
sudo hostname newname

# Permanently change hostname (edit /etc/hostname)
sudo nano /etc/hostname

# For immediate effect after editing
sudo /etc/init.d/hostname restart

Using FQDN in /etc/hostname might cause problems with:

• Certain services that expect only the short name
• Some configuration tools and scripts
• Logging systems

In some enterprise environments, you might need to configure /etc/hosts differently:

# For multi-homed systems
192.168.1.10 webserver.example.com webserver
10.0.0.10    webserver.internal.example.com webserver-int

Stick to the standard practice of using only the short hostname in /etc/hostname for Ubuntu 10.04. The FQDN belongs in other configuration files and DNS records.

In Ubuntu 10.04 (Lucid Lynx), the /etc/hostname file serves as the system's hostname configuration. This plain text file contains a single line specifying the machine's name. The traditional approach recommends using just the short hostname (e.g., "webserver") rather than the Fully Qualified Domain Name (FQDN, e.g., "webserver.example.com").

Ubuntu's official documentation for 10.04 clearly states:

# Recommended format for /etc/hostname
hostname

Not:

# Not recommended format
hostname.domain.tld

While the system might work with an FQDN in /etc/hostname, several components could malfunction:

• Some services may improperly parse the hostname
• System initialization scripts might behave unexpectedly
• Certain network utilities could generate incorrect output

For a server named "mail" in domain "example.com", the correct setup would be:

# /etc/hostname contents:
mail

# /etc/hosts contents:
127.0.0.1       localhost
192.168.1.10    mail.example.com mail

To check your current hostname settings:

# View system hostname
hostname

# View FQDN (requires proper DNS or hosts file)
hostname -f

# Check all name resolutions
getent hosts $(hostname)

To change the hostname properly:

# Edit the hostname file
sudo nano /etc/hostname

# Update hosts file
sudo nano /etc/hosts

# Apply changes without reboot
sudo hostname $(cat /etc/hostname)
sudo service hostname start

If you encounter problems after changing hostname:

1. Verify both /etc/hostname and /etc/hosts are consistent
2. Restart affected services: sudo service networking restart
3. Check syslog for errors: grep hostname /var/log/syslog