Using SD card only for the initial configuration: how eject it?

Other Hardware Storage
4

Another alternative:
Set a DoOnce variable at the start of the loop, have it open/read/close the file on the SD card, then set DoOnce again so it doesn't repeat it until next bootup.
Like:

int DoOnce;

void setup()
{
//Your code here
digitalWrite(13,HIGH);  //Optional status led
}

void loop()
{
if (DoOnce==0)
  {
    //Your code to open, read, and close here
  digitalWrite(13,LOW);  //Goes along with the Setup status led
  DoOnce=1;
  }
//Rest of your code
}