systemd Developer Lennart Poettering lennart@poettering.net nss-myhostname 8 nss-myhostname libnss_myhostname.so.2 Provide hostname resolution for the locally configured system hostname. libnss_myhostname.so.2 nss-myhostname is a plugin for the GNU Name Service Switch (NSS) functionality of the GNU C Library (glibc) primarily providing hostname resolution for the locally configured system hostname as returned by gethostname2. The precise hostnames resolved by this module are: The local, configured hostname is resolved to all locally configured IP addresses ordered by their scope, or -- if none are configured -- the IPv4 address 127.0.0.2 (which is on the local loopback) and the IPv6 address ::1 (which is the local host). The hostname localhost is resolved to the IP addresses 127.0.0.1 and ::1. The hostname gateway is resolved to all current default routing gateway addresses, ordered by their metric. This assigns a stable hostname to the current gateway, useful for referencing it independently of the current network configuration state. Various software relies on an always-resolvable local hostname. When using dynamic hostnames, this is traditionally achieved by patching /etc/hosts at the same time as changing the hostname. This is problematic since it requires a writable /etc file system and is fragile because the file might be edited by the administrator at the same time. With nss-myhostname enabled changing /etc/hosts is unncessary, and on many systems the file becomes entirely optional. To activate the NSS modules, myhostname has to be added to the line starting with hosts: in /etc/nsswitch.conf. It is recommended to place myhostname last in the nsswitch.conf line to make sure that this mapping is only used as fallback, and any DNS or /etc/hosts based mapping takes precedence. Here's an example /etc/nsswitch.conf file, that enables myhostname correctly: passwd: compat group: compat shadow: compat hosts: files dns mymachines myhostname networks: files protocols: db files services: db files ethers: db files rpc: db files netgroup: nis To test, use glibc's getent tool: $ getent ahosts `hostname` ::1 STREAM omega ::1 DGRAM ::1 RAW 127.0.0.2 STREAM 127.0.0.2 DGRAM 127.0.0.2 RAW In this case the local hostname is omega. systemd1, nss-mymachines8, nsswitch.conf5, getent1