Martins Blog

Trying to explain complex things in simple terms

Adding user equivalence for RAC the easy way

Posted by Martin Bach on December 22, 2010

This is the first time I am setting up a new 11.2.0.2 cluster with the automatic SSH setup. Until now, I ensured user equivalence by copying ssh RSA and DSA manually to all cluster nodes. For two nodes that’s not too bad, but recently someone asked a question around a 28 (!) node cluster on a mailing list I am subscribing to. So that’s when I think the whole process  gets a bit too labour intensive.

So setting up user equivalence using a script may be the solution. You can also use OUI to do the same, but I like to run “cluvfy stage -post hwos” to check everything is ok before even thinking about executing ./runInstaller.

Here’s the output of a session, my 2 cluster nodes are acfsprodnode1 and acfsprodnode2 (yes, they are for 11.2 ACFS replication and encryption testing). I am using the grid user as the owner of Grid Infrastructure, and oracle to own the RDBMS binaries. Start by navigating to the location where you unzipped the Grid Infrastructure patch file. Then change into directoy “sshsetup” and run the command:


[grid@acfsprdnode1 sshsetup]$ ./sshUserSetup.sh
Please specify a valid and existing cluster configuration file.
Either user name or host information is missing
Usage ./sshUserSetup.sh -user <user name> [ -hosts "<space separated hostlist>" | -hostfile <absolute path of cluster configuration file> ] [ -advanced ]  [ -verify] [ -exverify ] [ -logfile <desired absolute path of logfile> ] [-confirm] [-shared] [-help] [-usePassphrase] [-noPromptPassphrase]

Next execute the command, I opted for option noPromptPassphrase, as I don’t use them for the key.

[grid@acfsprdnode1 sshsetup]$ ./sshUserSetup.sh -user grid -hosts "acfsprdnode1 acfsprdnode2" -noPromptPassphrase
The output of this script is also logged into /tmp/sshUserSetup_2010-12-22-15-39-18.log
Hosts are acfsprdnode1 acfsprdnode2
user is grid
Platform:- Linux
Checking if the remote hosts are reachable
PING acfsprdnode1.localdomain (192.168.99.100) 56(84) bytes of data.
64 bytes from acfsprdnode1.localdomain (192.168.99.100): icmp_seq=1 ttl=64 time=0.017 ms
64 bytes from acfsprdnode1.localdomain (192.168.99.100): icmp_seq=2 ttl=64 time=0.019 ms
64 bytes from acfsprdnode1.localdomain (192.168.99.100): icmp_seq=3 ttl=64 time=0.017 ms
64 bytes from acfsprdnode1.localdomain (192.168.99.100): icmp_seq=4 ttl=64 time=0.017 ms
64 bytes from acfsprdnode1.localdomain (192.168.99.100): icmp_seq=5 ttl=64 time=0.018 ms

--- acfsprdnode1.localdomain ping statistics ---
5 packets transmitted, 5 received, 0% packet loss, time 3999ms
rtt min/avg/max/mdev = 0.017/0.017/0.019/0.004 ms
PING acfsprdnode2.localdomain (192.168.99.101) 56(84) bytes of data.
64 bytes from acfsprdnode2.localdomain (192.168.99.101): icmp_seq=1 ttl=64 time=0.331 ms
64 bytes from acfsprdnode2.localdomain (192.168.99.101): icmp_seq=2 ttl=64 time=0.109 ms
64 bytes from acfsprdnode2.localdomain (192.168.99.101): icmp_seq=3 ttl=64 time=0.324 ms
64 bytes from acfsprdnode2.localdomain (192.168.99.101): icmp_seq=4 ttl=64 time=0.256 ms
64 bytes from acfsprdnode2.localdomain (192.168.99.101): icmp_seq=5 ttl=64 time=0.257 ms

--- acfsprdnode2.localdomain ping statistics ---
5 packets transmitted, 5 received, 0% packet loss, time 4000ms
rtt min/avg/max/mdev = 0.109/0.255/0.331/0.081 ms
Remote host reachability check succeeded.
The following hosts are reachable: acfsprdnode1 acfsprdnode2.
The following hosts are not reachable: .
All hosts are reachable. Proceeding further...
firsthost acfsprdnode1
numhosts 2
<span style="color: #ff0000;">The script will setup SSH connectivity from the host acfsprdnode1 to all</span>
<span style="color: #ff0000;">the remote hosts</span>. After the script is executed, the user can use SSH to run
commands on the remote hosts or copy files between this host acfsprdnode1
and the remote hosts without being prompted for passwords or confirmations.

NOTE 1:
As part of the setup procedure, this script will use ssh and scp to copy
files between the local host and the remote hosts. Since the script does not
store passwords, you may be prompted for the passwords during the execution of
the script whenever ssh or scp is invoked.

NOTE 2:
AS PER SSH REQUIREMENTS, THIS SCRIPT WILL SECURE THE USER HOME DIRECTORY
AND THE .ssh DIRECTORY BY REVOKING GROUP AND WORLD WRITE PRIVILEDGES TO THESE
directories.

Do you want to continue and let the script make the above mentioned changes (yes/no)?
<span style="color: #ff0000;">yes</span>

The user chose yes
User chose to skip passphrase related questions.
Creating .ssh directory on local host, if not present already
Creating authorized_keys file on local host
Changing permissions on authorized_keys to 644 on local host
Creating known_hosts file on local host
Changing permissions on known_hosts to 644 on local host
Creating config file on local host
If a config file exists already at /home/grid/.ssh/config, it would be backed up to /home/grid/.ssh/config.backup.
Removing old private/public keys on local host
Running SSH keygen on local host with empty passphrase
Generating public/private rsa key pair.
Your identification has been saved in /home/grid/.ssh/id_rsa.
Your public key has been saved in /home/grid/.ssh/id_rsa.pub.
The key fingerprint is:
de:e3:66:fa:16:e8:6e:36:fd:c5:e3:77:75:07:9a:b0 grid@acfsprdnode1
Creating .ssh directory and setting permissions on remote host acfsprdnode1
THE SCRIPT WOULD ALSO BE REVOKING WRITE PERMISSIONS FOR group AND others ON THE HOME DIRECTORY FOR grid. THIS IS AN SSH REQUIREMENT.
The script would create ~grid/.ssh/config file on remote host acfsprdnode1. If a config file exists already at ~grid/.ssh/config, it would be backed up to ~grid/.ssh/config.backup.
The user may be prompted for a password here since the script would be running SSH on host acfsprdnode1.
Warning: Permanently added 'acfsprdnode1,192.168.99.100' (RSA) to the list of known hosts.
grid@acfsprdnode1's password:
Done with creating .ssh directory and setting permissions on remote host acfsprdnode1.
Creating .ssh directory and setting permissions on remote host acfsprdnode2
THE SCRIPT WOULD ALSO BE REVOKING WRITE PERMISSIONS FOR group AND others ON THE HOME DIRECTORY FOR grid. THIS IS AN SSH REQUIREMENT.
The script would create ~grid/.ssh/config file on remote host acfsprdnode2. If a config file exists already at ~grid/.ssh/config, it would be backed up to ~grid/.ssh/config.backup.
The user may be prompted for a password here since the script would be running SSH on host acfsprdnode2.
Warning: Permanently added 'acfsprdnode2,192.168.99.101' (RSA) to the list of known hosts.
grid@acfsprdnode2's password:
Done with creating .ssh directory and setting permissions on remote host acfsprdnode2.
Copying local host public key to the remote host acfsprdnode1
The user may be prompted for a password or passphrase here since the script would be using SCP for host acfsprdnode1.
grid@acfsprdnode1's password:
Done copying local host public key to the remote host acfsprdnode1
Copying local host public key to the remote host acfsprdnode2
The user may be prompted for a password or passphrase here since the script would be using SCP for host acfsprdnode2.
grid@acfsprdnode2's password:
Done copying local host public key to the remote host acfsprdnode2
cat: /home/grid/.ssh/known_hosts.tmp: No such file or directory
cat: /home/grid/.ssh/authorized_keys.tmp: No such file or directory
SSH setup is complete.

------------------------------------------------------------------------
Verifying SSH setup
===================
The script will now run the date command on the remote nodes using ssh
to verify if ssh is setup correctly. IF THE SETUP IS CORRECTLY SETUP,
THERE SHOULD BE NO OUTPUT OTHER THAN THE DATE AND SSH SHOULD NOT ASK FOR
PASSWORDS. If you see any output other than date or are prompted for the
password, ssh is not setup correctly and you will need to resolve the
issue and set up ssh again.
The possible causes for failure could be:
1. The server settings in /etc/ssh/sshd_config file do not allow ssh
for user grid.
2. The server may have disabled public key based authentication.
3. The client public key on the server may be outdated.
4. ~grid or ~grid/.ssh on the remote host may not be owned by grid.
5. User may not have passed -shared option for shared remote users or
may be passing the -shared option for non-shared remote users.
6. If there is output in addition to the date, but no password is asked,
it may be a security alert shown as part of company policy. Append the
additional text to the <OMS HOME>/sysman/prov/resources/ignoreMessages.txt file.
------------------------------------------------------------------------
--acfsprdnode1:--
Running /usr/bin/ssh -x -l grid acfsprdnode1 date to verify SSH connectivity has been setup from local host to acfsprdnode1.
IF YOU SEE ANY OTHER OUTPUT BESIDES THE OUTPUT OF THE DATE COMMAND OR IF YOU ARE PROMPTED FOR A PASSWORD HERE, IT MEANS SSH SETUP HAS NOT BEEN SUCCESSFUL. Please note that being prompted for a passphrase may be OK but being prompted for a password is ERROR.
Wed Dec 22 15:40:10 GMT 2010
------------------------------------------------------------------------
--acfsprdnode2:--
Running /usr/bin/ssh -x -l grid acfsprdnode2 date to verify SSH connectivity has been setup from local host to acfsprdnode2.
IF YOU SEE ANY OTHER OUTPUT BESIDES THE OUTPUT OF THE DATE COMMAND OR IF YOU ARE PROMPTED FOR A PASSWORD HERE, IT MEANS SSH SETUP HAS NOT BEEN SUCCESSFUL. Please note that being prompted for a passphrase may be OK but being prompted for a password is ERROR.
Wed Dec 22 15:40:10 GMT 2010
------------------------------------------------------------------------
SSH verification complete.
[grid@acfsprdnode1 sshsetup]$ ssh acfsprdnode1 hostname
acfsprdnode1
[grid@acfsprdnode1 sshsetup]$ ssh acfsprdnode2 hostname
acfsprodnode2
[grid@acfsprdnode1 sshsetup]$

Nice! That’s a lot of work taken away from me, and I can start runing cluvfy now to fix problems before OUI warns me about shortcomings on my system.

You should note that per the above output, the script only distributes the local ssh keys to the remote hosts. When in OUI’s cluster node addition screen (6 of 16 in the advanced installation) you still need to click on the “SSH Connectivity” button and then on “Setup” after providing username and password to establish cluster wide user equivalence.

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3 Responses to “Adding user equivalence for RAC the easy way”

  1. Leighton said

    Hi Martin,
    After using this method to setup ssh between a two-node cluster, CVU was able to pass the node connectivity tests. However, OUI fails to detect ssh configuration and you still have to do the automatic setup via OU.
    My guess is that OUI actually configures for ssh connectivity in both directions whereas the sshUserSetup.sh script only sets up ssh in one direction only.

    • Martin said

      It does! I initially wanted to update the post some time ago but never got around to do it. Thanks for brining it back to the radar! The section where the script tells you it’s taking the local ssh setup and distributes it across the cluster nodes is now highlighted in red, and also the fact that you still need to set the user equivalence up in OUI.

    • Roger said

      To setup in two directions add -advanced option

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