If you plan to install the QCG-Computing service on a separate machine (for performance or security reasons) you must assure that:
* the machine is a submit host of the batch system, what further implies that:
  * the machine share account information with the whole cluster (e.g. using LDAP or NIS),
  * the batch system/scheduler client packages are installed,
  * the QCG-Computing host is an authorized submit host
  * the host mounts some shared file system that is available on the worker node machines (however it does not have to be a HOME filesystem)

[[Image(DeploymentConcept.png)]]

Further sections gives some configuration hints for various batch system
== Torque and !Maui/Moab ==
* add qcg machine as submit host
{{{
  > qmgr
  Max open servers: 4
  Qmgr:
  set server submit_hosts += qcg.your.domain
  set server submit_hosts += qcg
}}}
**Note:** You may need to add the QCG-Computing host in the `/etc/hosts.equiv` file.

* the machine mounts `/home` filesystem of the cluster. Alternatively (or in addition) you can mount any other file system that can be used by any user (e.g. the scratch filesystem).
* the `PBS_SPOOL/server_logs` directory is exported in read-only mode (e.g. using NFS or Lustre) from Torque server to this machine (this share must be mounted locally as `PBS_SPOOL/server_logs`). The Torque DRMAA library for scalability reason can be configured to use batch system logs to get notified about jobs state changes.
* the `PBS_SPOOL/server_priv/accounting` directory is exported in read-only mode (e.g. using NFS or Lustre) from Torque server to this machine (this share must be mounted locally as `PBS_SPOOL/server_priv/accounting`). This file is used to determine exec hosts of short running (needed by BAT accounting).

* the machine is administrative host of the Maui Scheduler, what further denotes that:
 * The maui-client package is installed.
 * On the QCG-Computing machine modify the `SERVERHOST` section of the `/var/spool/maui/maui.cfg` file. It must points to the machine where the maui daemon is running.
 * On the Maui server machine modify the `ADMINHOSTS` section of the `/var/spool/maui/maui.cfg` file and add the QCG-Computing host to the list of admin hosts.


== Final Notes ==
**Note 1:** Although it is not mandatory we recommend you to restrict SSH access to the service machine by adding the following line to the `/etc/sshd_config` (remember to reload sshd deamon):
{{{
AllowUsers qcgadmin1 qcgadmin2 siteadmin otheradmin
}}}

**Note 2:** QCG service node should be treated as any other server machine in your cluster, i.e. don't forget about regular packages updates, general node monitoring used at site, security audits.