HP-UX Reference (11i v3 07/02) - 1M System Administration Commands A-M (vol 3)

m
mount_nfs(1M) mount_nfs(1M)
Background versus Foreground
File systems mounted with the bg option indicate that
mount is to retry in the background if the server’s
mount daemon does not respond. See mountd(1M).
mount retries the request up to the count specified in
the
retry=n option. Once the file system is mounted, each NFS request made in the kernel waits
timeo=n tenths of a second for a response. If no response arrives, the time-out is multiplied by
2 and the
request is retransmitted. When the number of retransmissions has reached the number specified in the
retrans=n option, a file system mounted with the
soft option returns an error on the request; one
mounted with the
hard option prints a warning message and continues to retry the request.
Hard versus Soft
File systems that are mounted read-write or that contain executable files should always be mounted with
the hard option. Applications using soft mounted file systems can incur unexpected I/O errors, file corr-
uption, unexpected program core dumps, and delays in system reboot/shutdown. The
soft option is not
recommended.
Authenticated requests
The server can require authenticated NFS requests from the client.
sec=dh authentication might be
required. See nfssec(5).
URLs and the public Option
If the
public option is specified, or if the resource includes an NFS URL,
mount attempts to connect to
the server using the public file handle lookup protocol. See WebNFS Client Specification, RFC 2054. If the
server supports the public file handle, the attempt is successful;
mount does not need to contact the
server’s rpcbind(1M) and the mountd(1M) daemons to get the port number of the
mount server and the
initial file handle of pathname, respectively. If the NFS client and server are separated by a firewall that
allows all outbound connections through specific ports, such as
NFS_PORT, then this enables NFS opera-
tions through the firewall. The public option and the NFS URL can be specified independently or
together. They interact as specified in the following matrix:
resource style
host:pathname NFS URL
Force public file handle and fail
mount if not supported.
Use Native paths.
Force public file handle and fail
mount if not supported.
Use Canonical paths.
public option
Try public file handle with Canoni-
cal paths. Fall back to MOUNT
protocol if not supported.
default Use MOUNT protocol.
A Native path is a path name that is interpreted according to conventions used on the native operating sys-
tem of the NFS server. A Canonical path is a path name that is interpreted according to the URL rules.
See Uniform Resource Locators (URL), RFC 1738. See EXAMPLES for uses of Native and Canonical paths.
Replicated File Systems and Failover
resource can list multiple read-only file systems to be used to provide data. These file systems should con-
tain equivalent directory structures and identical files. It is also recommended that they be created by a
utility such as rdist(1). The file systems can be specified either with a comma-separated list of
host:/pathname entries and/or NFS URL entries, or with a comma -separated list of hosts, if all file sys-
tem names are the same. If multiple file systems are named and the first server in the list is down, failover
uses the next alternate server to access files. If the read-only option is not chosen, mount fails. Note that
the llock option is always used for replicated servers.
File Attributes
To improve NFS read performance, files and file attributes are cached. File modification times get updated
whenever a write occurs. However, file access times can be temporarily out-of-date until the cache gets
refreshed.
The attribute cache retains file attributes on the client. Attributes for a file are assigned a time to be
flushed. If the file is modified before the flush time, then the flush time is extended by the time since the
last modification (under the assumption that files that changed recently are likely to change soon). There is
a minimum and maximum flush time extension for regular files and for directories. Setting actimeo=n
sets flush time to n seconds for both regular files and directories.
544 Hewlett-Packard Company − 4 − HP-UX 11i Version 3: February 2007