Linux hostnamectl Command

Hostname Configuration

• The hostnamectl command can be used to set the hostname of a system.
• The --transient option sets the transient hostname, which is not stored in any file.
• The --static option sets the static hostname, which is stored in the /etc/hostname file.

Displaying System Information

• The hostnamectl command can also be used to display various descriptive and identity bits of information about the running system, including:
  • Static hostname
  • Pretty hostname
  • Transient hostname
  • Icon name
  • Chassis
  • Machine ID
  • Boot ID
  • Operating System
  • Kernel
  • Architecture

Name Resolution

• There are two basic ways to match names and IP numbers: using a local source or a remote server.
• The hosts database keeps track of the mapping between host names and host numbers.
• The /etc/hosts file can be modified to associate multiple names with a single IP address.
• The /etc/nsswitch.conf file defines the priority order of the sources for name-IP matches.

Networking Fundamentals

• Linux expects TCP/IP settings to be in specific places and may need to be changed when the default settings are not appropriate.
• The ip link show and nmcli device commands can be used to list the network adapters present in the system.
• The /etc/network/interfaces file is used by the ifup command to activate interfaces during boot time.
• The /etc/nsswitch.conf file is used by the system and applications to determine the sources for name-service information in a range of categories, called databases.

Persistent Network Configuration

• Files in /etc/systemd/network can be used to override the configurations in /lib/systemd/network.
• Files with a .netdev suffix are used by systemd-networkd to create virtual network devices, such as bridge or tun devices.
• Files with a .link suffix set low-level configurations for the corresponding network interface.
• Files with a .network suffix can be used to set up network addresses and routes.

Network Troubleshooting

• The ip command can be used to manually configure network interfaces, including viewing and changing the configuration of network interfaces.
• The ip command can also be used to manually configure routing, including viewing and changing routing tables and setting the default route.
• The tracepath command can be used to troubleshoot network connections and detect the smallest MTU on the entire link.
• The nc command can be used to send or receive arbitrary data over a TCP or UDP network connection.