nss-myhostname

systemd
Developer Lennart Poettering lennart@poettering.net
nss-myhostname 8
nss-myhostname Provide hostname resolution for the locally configured system hostname.

`nss-myhostname.la`

## Description

`nss-myhostname` is a plugin for the GNU Name Service Switch (NSS) functionality of the GNU C Library (`glibc`) providing hostname resolution for the locally configured system hostname as returned by gethostname 2. Various software relies on an always-resolvable local hostname. When using dynamic hostnames, this is usually achieved by patching `/etc/hosts` at the same time as changing the host name. This however is not ideal since it requires a writable `/etc` file system and is fragile because the file might be edited by the administrator at the same time. `nss-myhostname` simply returns all locally configured public IP addresses, 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) for whatever system hostname is configured locally. Patching `/etc/hosts` is thus no longer necessary.

To activate the NSS modules, `myhostname` has to be added to the line starting with "`hosts:`" in `/etc/nsswitch.conf`

It is recommended to put `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.

## Example

    # /etc/nsswitch.conf

    passwd:         compat
    group:          compat
    shadow:         compat

    hosts:          files dns 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`.

## See Also

systemd 1, systemd-logind.service 8, logind.conf 5, loginctl 1, pam.conf 5, pam.d 5, pam 8, pam_loginuid 8