gpssh-exkeys

Exchanges SSH public keys between hosts.

Synopsis

  1. gpssh-exkeys -f <hostfile_exkeys> | -h <hostname> [-h <hostname> ...]
  3. gpssh-exkeys -e <hostfile_exkeys> -x <hostfile_gpexpand>
  5. gpssh-exkeys -? 
  7. gpssh-exkeys --version

Description

The gpssh-exkeys utility exchanges SSH keys between the specified host names (or host addresses). This allows SSH connections between Greenplum hosts and network interfaces without a password prompt. The utility is used to initially prepare a Greenplum Database system for passwordless SSH access, and also to prepare additional hosts for passwordless SSH access when expanding a Greenplum Database system.

Keys are exchanged as the currently logged in user. You run the utility on the master host as the gpadmin user (the user designated to own your Greenplum Database installation). Greenplum Database management utilities require that the gpadmin user be created on all hosts in the Greenplum Database system, and the utilities must be able to connect as that user to all hosts without a password prompt.

You can also use gpssh-exkeys to enable passwordless SSH for additional users, root, for example.

The gpssh-exkeys utility has the following prerequisites:

  • The user must have an account on the master, standby, and every segment host in the Greenplum Database cluster.
  • The user must have an id_rsa SSH key pair installed on the master host.
  • The user must be able to connect with SSH from the master host to every other host machine without entering a password. (This is called “1-n passwordless SSH.”)

You can enable 1-n passwordless SSH using the ssh-copy-id command to add the user’s public key to each host’s authorized_keys file. The gpssh-exkeys utility enables “n-n passwordless SSH,” which allows the user to connect with SSH from any host to any other host in the cluster without a password.

To specify the hosts involved in an SSH key exchange, use the -f option to specify a file containing a list of host names (recommended), or use the -h option to name single host names on the command-line. At least one host name (-h) or a host file (-f) is required. Note that the local host is included in the key exchange by default.

To specify new expansion hosts to be added to an existing Greenplum Database system, use the -e and -x options. The -e option specifies a file containing a list of existing hosts in the system that have already exchanged SSH keys. The -x option specifies a file containing a list of new hosts that need to participate in the SSH key exchange.

The gpssh-exkeys utility performs key exchange using the following steps:

  • Adds the user’s public key to the user’s own authorized_keys file on the current host.
  • Updates the known_hosts file of the current user with the host key of each host specified using the -h, -f, -e, and -x options.
  • Connects to each host using ssh and obtains the user’s authorized_keys, known_hosts, and id_rsa.pub files.
  • Adds keys from the id_rsa.pub files obtained from each host to the authorized_keys file of the current user.
  • Updates the authorized_keys, known_hosts, and id_rsa.pub files on all hosts with new host information (if any).

Options

-e hostfile_exkeys

When doing a system expansion, this is the name and location of a file containing all configured host names and host addresses (interface names) for each host in your current Greenplum system (master, standby master, and segments), one name per line without blank lines or extra spaces. Hosts specified in this file cannot be specified in the host file used with -x.

-f hostfile_exkeys

Specifies the name and location of a file containing all configured host names and host addresses (interface names) for each host in your Greenplum system (master, standby master and segments), one name per line without blank lines or extra spaces.

-h hostname

Specifies a single host name (or host address) that will participate in the SSH key exchange. You can use the -h option multiple times to specify multiple host names and host addresses.

–version

Displays the version of this utility.

-x hostfile_gpexpand

When doing a system expansion, this is the name and location of a file containing all configured host names and host addresses (interface names) for each new segment host you are adding to your Greenplum system, one name per line without blank lines or extra spaces. Hosts specified in this file cannot be specified in the host file used with -e.

-? (help)

Displays the online help.

Examples

Exchange SSH keys between all host names and addresses listed in the file hostfile_exkeys:

  1. $ gpssh-exkeys -f hostfile_exkeys

Exchange SSH keys between the hosts sdw1, sdw2, and sdw3:

  1. $ gpssh-exkeys -h sdw1 -h sdw2 -h sdw3

Exchange SSH keys between existing hosts sdw1, sdw2, and sdw3, and new hosts sdw4 and sdw5 as part of a system expansion operation:

  1. $ cat hostfile_exkeys
  2. mdw
  3. mdw-1
  4. mdw-2
  5. smdw
  6. smdw-1
  7. smdw-2
  8. sdw1
  9. sdw1-1
  10. sdw1-2
  11. sdw2
  12. sdw2-1
  13. sdw2-2
  14. sdw3
  15. sdw3-1
  16. sdw3-2
  17. $ cat hostfile_gpexpand
  18. sdw4
  19. sdw4-1
  20. sdw4-2
  21. sdw5
  22. sdw5-1
  23. sdw5-2
  24. $ gpssh-exkeys -e hostfile_exkeys -x hostfile_gpexpand

See Also

gpssh, gpscp