I'm trying to build a small cluster of pi's and am using mpich2 to run parallel code. It appears mpich2 has installed ok and I'm able to ssh into both (I'm starting with 2) pi's. However when I run a program using mpich2 it makes me enter the passphrase for my rsa key pair 2 times then I have to enter the password for the other pi 3 times, each time having to press enter twice. According to this tutorial I should only have to enter those passwords once. However every time I run mpich2 it makes me enter the passwords. Does anyone have any suggestions?

2 Answers 2


You need to have a SSH agent running that can remember your password. If ps u -C ssh-agent does not show any running processes, check your distribution documentation for installation details.

When you have installed it, I suggest you store the passphrase with an expiration date. For instance, store the default keys for an hour:

ssh-add -t 3600

If you need to store just a single key, or a key with an odd name, use something like:

ssh-add -t 3600 ~/.ssh/id_rsa

The currently active keys are visible with ssh-add -l. Now you can ssh into Pi's without constantly having to enter a passphrase.


did you enter any passphrase when generating your RSA keys? if yes, you have to create new keys, without a passphrase, otherwise you'll need to enter it everytime.

  • I understand entering it every time now but it asks me like 3-4 times. should it be doing that?
    – Slayter
    Commented May 13, 2013 at 1:57
  • @Slayter please, read your tutorial carefully, it says: "If you leave this blank (not such good security) then no further typing of passphrases is needed."
    – lenik
    Commented May 13, 2013 at 9:24

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