For many customers I work with SSH won't be available between the OEM and monitoring hosts. Therefore you cannot push the management agent on to the host from the OEM console. Customer might have to raise CR to allow SSH between the hosts but this might take a while and it's really unnecessary.
In that case the management agent has to be installed in silent mode. That is when the agent won't be pushed from OEM to the host but pulled by the host and installed. There are thrее ways to do that - using AgentPull script, agentDeploy script or using RPM file.
When using AgentPull script, you download a script from the OMS and then run it. It will download the agent package and install it on the local host. Using the agentDeploy script is very similar but to obtain it you use EMCLI. The third method of using RPM file is similar - using EMCLI you download RPM file and install it on the system. These methods require HTTP/HTTPS access to the OMS, AgentDeploy and RPM file also require ELICLI to be installed. For that reason I always use AgentPull method since it's quicker and really straight forward. Another benefit of using AgentPull method is that if you don't have HTTP/HTTPS access to the OEM you can simply copy and paste the script.
Download a script from the OEM first, use curl or wget. The monitoring hosts usually don't have HTTP access but many of them do so by using HTTP proxy. Download the script and make it executable:
curl "https://oem13c.local.net:7802/em/install/getAgentImage" --insecure -o AgentPull.sh chmod +x AgentPull.sh
If a proxy server is not available then you can simply copy and paste the script, the location of the script on the OEM server is:
Make sure you edit the file change the oms host and oms port parameters.
Check what are the available platforms:
[oracle@exa01db01 ~]$ ./AgentPull.sh -showPlatforms Platforms Version Linux x86-64 126.96.36.199.0
Run the script by suppling the sysman password, platform you want to install, agent registration password and the agent base directory:
[oracle@exa01db01 ~]$ ./AgentPull.sh LOGIN_USER=sysman LOGIN_PASSWORD=welcome1 PLATFORM="Linux x86-64" AGENT_REGISTRATION_PASSWORD=welcome1 AGENT_BASE_DIR=/u01/app/oracle/agent13c
It takes less than two minutes to install the agent and then at the end you'll see the following messages:
Agent Configuration completed successfully The following configuration scripts need to be executed as the "root" user. Root script to run : /u01/app/oracle/agent13c/agent_188.8.131.52.0/root.sh Waiting for agent targets to get promoted... Successfully Promoted agent and its related targets to Management Agent
Now login as root and run the root.sh file.
To be honest, I use this method regardless of the circumstances, it's so much easier and faster.