nss-myhostname

systemd
Developer Lennart Poettering lennart@poettering.net
nss-myhostname 8
nss-myhostname Provide host name 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 host name resolution for the locally configured system hostname as returned by gethostname 2. Various software relies on an always resolvable local host name. 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 configure 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 host name 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