Red Hat ENTERPRISE LINUX 3 Reference Manual page 132

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Warning
NFS mount privileges are granted to the client host, not the user. Therefore, exported file systems
can be accessed by any user on a client host with access permissions. When configuring the NFS
shares, be very careful which hosts get read/write permissions (
9.1.1. Required Services
Red Hat Enterprise Linux uses a combination of kernel-level support and daemon processes to provide
NFS file sharing. NFS relies on Remote Procedure Calls (RPC) to route requests between clients and
servers . RPC services under Linux are controlled by the
file systems, the following services work together:
— Starts the appropriate RPC processes to service requests for shared NFS file systems.
• nfs
— An optional service that starts the appropriate RPC processes to allow NFS clients to
• nfslock
lock files on the server.
— The RPC service for Linux; it responds to requests for RPC services and sets up
• portmap
connections to the requested RPC service.
The following RPC processes work together behind the scenes to facilitate NFS services:
— This process receives mount requests from NFS clients and verifies the requested
• rpc.mountd
file system is currently exported. This process is started automatically by the
not require user configuration.
— This process is the NFS server. It works with the Linux kernel to meet the dynamic
•
rpc.nfsd
demands of NFS clients, such as providing server threads each time an NFS client connects. This
process corresponds to the
— An optional process that allows NFS clients to lock files on the server. This process
•
rpc.lockd
corresponds to the
— This process implements the Network Status Monitor (NSM) RPC protocol which
• rpc.statd
notifies NFS clients when an NFS server is restarted without being gracefully brought down. This
process is started automatically by the
— This process provides user quota information for remote users. This process is
• rpc.rquotad
started automatically by the
9.1.2. NFS and
portmap
The service under Linux maps RPC requests to the correct services. RPC processes notify
portmap
when they start, revealing the port number they are monitoring and the RPC program num-
portmap
bers they expect to serve. The client system then contacts
RPC program number. The
communicate with the requested service.
Because RPC-based services rely on
must be available before any of these services start.
portmap
The service uses TCP wrappers for access control, and access control rules for
portmap
affect all RPC-based services. Alternatively, it is possible to specify access control rules for each of the
NFS RPC daemons. The man pages for
the precise syntax for these rules.
service.
nfs
service.
nfslock
nfslock
service and does not require user configuration.
nfs
service redirects the client to the proper port number so it can
portmap
portmap
rpc.mountd
Chapter 9. Network File System (NFS)
rw
portmap
service and does not require user configuration.
portmap
to make all connections with incoming client requests,
and
rpc.statd
).
service. To share or mount NFS
service and does
nfs
on the server with a particular
contain information regarding
portmap