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| = nsswitch.conf = | = NsSwitch.Conf = The '''Name Service Switch configuration file''' (or '''`nsswitch.conf(5)`'''), typically found at `/etc/nsswitch.conf`, declares how domain names should be translated into [[Protocols/IP|IP addresses]]. |
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| The first column (delimited by spaces or tab characters) indicates a database, while every subsequent column is a source. Some common database sources are listed below. | The first column (delimited by spaces or tab characters) indicates a '''database''', while every subsequent column is a '''service specification''' or '''optional action'''. |
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| For `hosts`... | === Service Specifications === Common service specifications are: |
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| * `dns` (i.e. run-time lookups based on `/etc/resolv.conf`) | * `dns` (i.e. runtime lookups based on `/etc/resolv.conf`) |
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| * `mymachine` which connects to `systemd-machined` (see `nss-mymachines(8)`) * `resolve` which connects to `systemd-resolved` (see `nss-resolve(8)`) |
* `mymachine` which connects to [[Linux/Systemd|systemd-machined]] (see `nss-mymachines(8)`) * `resolve` which connects to [[Linux/SystemdResolved|systemd-resolved]] (see `nss-resolve(8)`) === Optional Actions === Option actions follow the pattern of `[STATUS=ACTION]` and `[!STATUS=ACTION]`. A '''status''' can be any of: * `success` meaning 'no error'. * `notfound` meaning 'error in lookup'. * `unavail` indicates a connection couldn't be made. * `tryagain` indicates 'temporarily unavailability', as with locked connections. An '''action''' can be any of: * `return` meaning 'return the result' * `continue` meaning 'try the next item' * `merge` causes the system to try both the preceding and the following items By default, only a `success` status results in a `return` action. Anything else will result in a `continue`. The exception the `group` database, where a `notfound` status will lead to a `continue` action regardless of any action specified. |
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| === Action Items === | == See also == |
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| '''Action items''' follow one the following patterns: `[STATUS=ACTION]` and `[!STATUS=ACTION]`. `STATUS` can be any of... * `success` meaning 'no error'. * `notfound` meaning 'error in lookup'. * `unavail` indicates a connection couldn't be made. * `tryagain` indicates 'temporarily unavailability', as with locked connections. `ACTION` can be any of... * `return` meaning 'return the result' * `continue` meaning 'try the next item' * `merge` causes the system to try both the preceding and the following items, and By default, only a `success` status results in a `return` action. Anything else will result in a `continue`. The exception is for a `group` lookup-a `notfound` status will lead to a `continue` action regardless of any action specified. |
[[https://man.archlinux.org/man/nsswitch.conf.5|nsswitch.conf(5)]] |
NsSwitch.Conf
The Name Service Switch configuration file (or nsswitch.conf(5)), typically found at /etc/nsswitch.conf, declares how domain names should be translated into IP addresses.
Example
passwd: compat group: compat shadow: compat hosts: dns [!UNAVAIL=return] files networks: nis [NOTFOUND=return] files ethers: nis [NOTFOUND=return] files protocols: nis [NOTFOUND=return] files rpc: nis [NOTFOUND=return] files services: nis [NOTFOUND=return] files
Syntax
Databases
The first column (delimited by spaces or tab characters) indicates a database, while every subsequent column is a service specification or optional action.
Service Specifications
Common service specifications are:
files (i.e. /etc/hosts)
dns (i.e. runtime lookups based on /etc/resolv.conf)
myhostname (see nss-myhostname(8))
mymachine which connects to systemd-machined (see nss-mymachines(8))
resolve which connects to systemd-resolved (see nss-resolve(8))
Optional Actions
Option actions follow the pattern of [STATUS=ACTION] and [!STATUS=ACTION].
A status can be any of:
success meaning 'no error'.
notfound meaning 'error in lookup'.
unavail indicates a connection couldn't be made.
tryagain indicates 'temporarily unavailability', as with locked connections.
An action can be any of:
return meaning 'return the result'
continue meaning 'try the next item'
merge causes the system to try both the preceding and the following items
By default, only a success status results in a return action. Anything else will result in a continue. The exception the group database, where a notfound status will lead to a continue action regardless of any action specified.