I'm running SmKeytool and this one doesn't seem to work in the linux
based Policy Server. When I run it, it gives error :

  Error: Could not find or load main class com.netegrity.smkeydatabase.db.SMKeytool

When I am trying to get the metadata for the IDP, I am not able to run
the ./smkeytool.sh which throw error as shown above.

I have tried running ca_ps_env.sh then I can see same issue. 

How can I fix it ?

Policy Server 12.8SP2 on RedHat 7;

You should note that the smkeytool.sh is to manage the certificates
from the certificates store.

I've just tried in my lab, I've reproduced the issue and I've fixed it :

  I reproduced the issue that way :

  [ps.training.com] root :: 08:28:36 : /opt/CA/siteminder/bin $ ./smkeytool.sh
  Error: Could not find or load main class com.netegrity.smkeydatabase.db.SMKeytool

and here are the steps to fix it, you need to have the environment
variables set to get the command to run properly :

  [ps.training.com] root :: 08:28:44 : /opt/CA/siteminder/bin $ cd ..
  [ps.training.com] root :: 08:29:13 : /opt/CA/siteminder $ source ca_ps_env.ksh
  [ps.training.com] root :: 08:23:48 : /opt/CA/siteminder $ Version
  [Version -  Version 12.8.0200.1992]

  [ps.training.com] root :: 08:23:51 : /opt/CA/siteminder $ smkeytool.sh -listCerts

  [...]

  Alias Name: jsmithca
  Type: CertificateAuthorityEntry
  Subject: CN=jsmith,OU=Support,O=Broadcom,L=Barcelona,ST=Barcelona,C=ES
  Issuer: CN=jsmith,OU=Support,O=Broadcom,L=Barcelona,ST=Barcelona,C=ES
  Serial Number: 00C4CDAEA1A25AF6C4
  Valid from: Fri May 17 12:08:44 CEST 2019  until: Mon May 14 12:08:44 CEST 2029

  *****************************************************************************

  [...]

  *****************************************************************************

  Number of entries listed: 8.

  [ps.training.com] root :: 08:26:00 : /opt/CA/siteminder $ smkeytool.sh -help

  Certificate Data Store Management Tool!
  SMKeytool Usage:

  [...]