which one is valid?

[hemmin]

The command display configuration is used to duplicate the configuration data from the Flash memory of the active control card to Flash memory of the standby one.

The command display configuration is used for duplicating duplicate the configuration data from the Flash memory of the active control card to Flash memory of the standby one.

What is the difference? Used to / used for? Which one is valid and why?

[eflnow]

"Used to + inf. verb" refers to a repetitive or habitual action in the past which no longer occurs in the present e.g I used to smoke. (This means the subject has quit smoking).

"to be used for" is the passive form of the verb "to use". Since we are trying to explain the purpose of the display configuration this verb form is the "valid" choice.

n.b. In your second sentence there's a redundancy: ...duplicating duplicate(??)....