In general, use SSH to accomplish secure remote command execution. You create a public/private keypair for each user and distribute that user's public keys to all the other machines. Then you can securely have root log into another root host.
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What security issues can I potentially have with the above approach?
Many. If the "privileged command" can be tricked or fooled in some way, the security will be broken. If the "privileged command" is actually a script, there's a good chance this can be broken no matter what. If the command takes input from the user, there's a possibility the security can be broken. On the other hand, doing this is much better than allowing a user root access or allowing the user to run a script with sudo.
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Is there other obvious (standard??) way to invoke privileged commands remotely that do not require some sort of agent running on each server? (Do I need an agent on each box??)
Yes, but rsh is deemed broken by nearly all security experts. It works fairly well, however, in a LAN not connected to the internet and in which every NIC is using IPSEC or every port is locked to a MAC-Address, and in which all hostnames are kept statically on the /etc/hosts file of every hosts.
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Would the new feature of Solaris 10 privileges help me in any way?[/QUOTE]
Yes, but they would not work in a heterogeneous network (mixed with other OS's).