For example, you can configure a network interface and other settings from the command line of your terminal. But you can also save the settings to the file /etc/network/interfaces (Debian GNU/Linux) or appropriate of NetworkManager.

Another example, if you want to add a permanent entry to the ARP table of FreeBSD, you should execute the command:

# arp -S 01:23:45:ab:cd:ef

or add to rc.conf the following:

static_arp_gw=" 01:23:45:ab:cd:ef"

Similar examples are numerous. The result takes effect immediately when you use the first method. With the second method, you must restart your system completely or only appropriate service.

Is there a name for the first method as a single word or abbreviation? As far as I remember there is a more precise term and I stumbled on it somewhere.

  • 1
    temporary/volatile/transient/non-permanent/... settings vs. permanent/persistent/non-volatile/non-transient/... settings?
    – Dubu
    May 14, 2014 at 13:54
  • 1
    declarative vs. imperative? You always need an imperative configuration command (i.e. arp) to make a non-permanent change to a running instance. When declarative configuration is the only kind available, you're forced to put your change somewhere permanent even if you don't want it to persist.
    – user41515
    May 15, 2014 at 15:42
  • @all Well, the above comments are not bad answers.
    – Apostle
    May 18, 2014 at 22:13
  • @Dubu Your comment is not a bad answer.
    – Apostle
    May 21, 2014 at 11:19
  • @WumpusQ.Wumbley Your comment is not a bad answer.
    – Apostle
    May 21, 2014 at 11:20

1 Answer 1


The same tool is used to do the configuring in all three cases, ifconfig.

ifconfig is a system administration utility in Unix-like operating systems for network interface configuration.

The utility is a command line interface tool and is also used in the system startup scripts of many operating systems. It has features for configuring, controlling, and querying TCP/IP network interface parameters. Ifconfig originally appeared in 4.2BSD as part of the BSD TCP/IP suite.

So I would describe your 3 approaches as follows:

  1. Manually configuring a network interface using ifconfig. This is a one time setup that will not persist between reboots.
  2. Manually configuring a network interface using startup configuration files. This approach will persist between reboots and automatically configure the network interface upon each boot. During a boot there are services/scripts that will parse the contents of the Interfaces file and call ifconfig to set them up.
  3. Using NetworkManager is a frontend to the management of the Interfaces file. There are other options, such as wicd which serve the same purpose.

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