mountd - NFS mount daemon


/usr/sbin/rpc.mountd [ -f exports-file? [ -d facility? [ -P port? [ -Dhnprv? [ --debug facility? --exports-file=file? [ --help? [ --allow-non-root? --re-export? [ --no-spoof-trace? [ --version?


The mountd program is an NFS mount daemon. When receiving a MOUNT request from an NFS client, it checks the request against the list of exported file systems listen in /etc/exports. If the client is permitted to mount the file system, mountd creates a file handle for the requested directory, and adds an entry /etc/rmtab. Upon receipt of an UMOUNT request, it removes the client's entry from rmtab. Note, however, that a client may still be able to use the file handle after the UMOUNT request (for instance, if the client mounts the same remote file system on two different mount points). Similarly, if a client reboots without notifying mountd, a stale entry will remain in rmtab.

Running from inetd

mountd can be started from inetd rather than at system boot time by adding the following two lines to /etc/inetd.conf:

mount/1-2 dgram rpc/udp wait root /usr/sbin/rpc.mountd rpc.mountd mount/1-2 stream rpc/tcp wait root /usr/sbin/rpc.mountd rpc.mountd When run from inetd, mountd will terminate after a certain period of inactivity.


-f or --exports-file

This option specifies the exports file, listing the clients that this server is prepared to serve and parameters to apply to each such mount (see exports(5)). By default exports are read from /etc/exports.

-d or --debug

Log each transaction verbosely to standard error. Valid log facilities are call for the logging of all calls, auth for client authentication, fhcache for operations of the file handle cache, and rmtab for manipulation of /etc/rmtab. By default, log output is sent to syslogd unless the daemon runs in the foreground.

-F or --foreground

Unlike normal in operation, mountd will not detach from the terminal when given this option. When debugging is requested, it will be sent to standard error.

-h or --help

Provide a short help summary.

-n or --allow-non-root

Allow incoming mount requests to be honored even if they do not originate from reserved IP ports. Some older NFS client implementations require this. Some newer NFS client implementations don't believe in reserved port checking.

-P portnum or --port portnum

Makes mountd listen on port portnum instead of some random port. By default, mountd will listen on the mount/udp port specified in /etc/services, or, if that is undefined, on some arbitrary port number below 1024.

-p or --promiscuous

Put the server into promiscuous mode where it will serve any host on the network.

-r or --re-export

Allow imported NFS or SMB file-systems to be exported. This can be used to turn a machine into an NFS/SMB multiplier. Caution should be used when re-exporting loopback mounts because re-entering the mount point will result in deadlock between the client file system code and the server.

-t or --no-spoof-trace

By default, mountd logs every access by unauthorized clients. This option turns off logging of such spoof attempts for all hosts listed explicitly in the exports file.

-v or --version

Report the current version number of the program.

Access Control

For enhanced security, access to mountd can be limited via the TCP wrapper library that's part of Wietse Venema's tcp_wrappers package. Support for this option must be selected at compile time. In order to restrict access to all hosts on your local network (say, you would add the following lines to your /etc/hosts.allow file:

rpc.mountd : 192.168.1. : allow rpc.mountd : ALL : deny This example assumes your TCP wrapper library was compiled with options support (which I highly recommend). If it has been compiled without options support, you need to add the following two lines to /etc/hosts.allow and /etc/hosts.deny, respectively:

''# hosts.allow: rpc.mountd : 192.168.1

  1. hosts.deny

rpc.mountd : ALL When changing this information, you must restart mountd'' for these changes to take effect, either by killing and restarting, or by sending it the HUP signal.


The information in /etc/rmtab is inaccurate more often than not.


When receiving a SIGHUP, mountd will re-read the exports file and any access restrictions defined in the /etc/hosts.allow and /etc/hosts.deny file. Note that to make export changes take effect, you have to send nfsd a SIGHUP as well.


/etc/exports /etc/rmtab


exports(5), nfsd(8)?, ugidd(8C), showmount(8).

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