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User Unable to SSH into the Master when using NFS Mounted Home Directories

Environment

  • Pivotal Greenplum Database (GPDB) 4.2.x
  • Operating System- All supported

Symptom

Following scenario occurs:

  • Users unable to login via SSH, but ESRS login is working fine.
  • The database is up and running.
  • Any SSH command from external users is hanging.

Cause

Home directories on the master server (i.e MDW) are mounted on the NFS. Upon SSH login, SSH needs to access files in the user home directory to authenticate the login.

In case the NFS system is busy or hanging (Example: Overloaded by a huge COPY table out to home directory), then SSH logins does not work. When the COPY command terminates, it overwhelms the NFS and becomes a defunct process and ultimately gets stuck in the kernel call.

Resolution

A quick way to check for this is:

  • df -h on the master takes a very long time to return to the NFS mounted home directories.
  • SSH using verbose shows connection is waiting on the RSA key for authentication on the directory which is on the NFS share.

To fix this issue, unmount and remount the NFS shared directories.

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