Hostname / Host ID

Commands

cat /proc/sys/kernel/hostname	Hostname directly from the kernel's hostname file.
hostname	Displays the hostname.
uname -n	Displays just the hostname.
hostnamectl	*systemd systems - Most comprehensive hostname info
cat /etc/hostname	Displays the hostname stored in the /etc/hostname file.
hostid	Prints the numeric identifier for the current host.

Multiple hostnames: A system can have different hostnames configured for various purposes.

Static vs. Transient

hostnamectl distinguishes between static (set in configuration files) and transient (set at runtime) hostnames.

File Locations

/etc/hostname	On many Linux distributions such as Debian and Ubuntu, stores the system's hostname.
/etc/hosts	Contains mappings of IP addresses to hostnames, often includes the system's hostname for the loopback interface.
/etc/sysconfig/network	On Red Hat-based distributions like Red Hat Enterprise Linux (RHEL) and CentOS, sets the system's hostname.
/etc/rc.conf or /etc/rc.conf.local	On some Unix systems like FreeBSD, stores the hostname information.
Dynamic Host Configuration Protocol	In network configurations using DHCP, the hostname may be assigned dynamically by the DHCP server.
hostname command	Used to view or change the hostname temporarily during a session.
Network Configuration Files	Some Unix distributions store hostname information in network configuration files.
NIS/NIS+	In network environments using NIS or NIS+ for centralized authentication and configuration management.