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mount_nfs(1m) [hpux man page]

mount_nfs(1M)															     mount_nfs(1M)

NAME
mount_nfs: mount, umount - mount and unmount remote NFS resources SYNOPSIS
specific_options] resource mount_point {resource|mount_point} DESCRIPTION
This manpage describes only the NFS-specific and commands. See mount(1M) for the description of the non-NFS commands. The utility attaches a named resource to the file system hierarchy at the pathname location mount_point, which must already exist. If mount_point has any contents prior to the operation, the contents remain hidden until the resource is once again unmounted. Only a superuser can mount file systems. The utility unmounts mounted file systems. Only a superuser can unmount file systems. resource can be of the form: The host can be the name of the NFS server host, or an IPv4 or IPv6 address string. As IPv6 addresses already contain colons, enclose host in a pair of square brackets when specifying an IPv6 address string. Otherwise, the first occurrence of a colon can be interpreted as the separator between the host name and path; for example: See IPv6(7P). pathname is the path name of the directory on the server being mounted. The path name is interpreted according to the server's path name parsing rules, and the path name is not necessarily slash-separated. However, on most servers, the path name is slash- separated. Specify an NFS URL and follow the standard convention for NFS URL as described in See the discussion of URL's and the option under section below for a more detailed discussion. A comma-separated list of: or See the discussion on under for a more detailed discussion. A comma-separated list of: hosts followed by a suffix. See the discussion on under for a more detailed discussion. Options (mount) See mount(1M) for the description of the options. Note that the option only accepts either or forces the use of NFS Version 3 unless the option is used. The options are as follows: Print debug messages to stderr. This option is to be used by HP support engineers. These specific_options are NFS-specific only. Set file system specific options according to a comma-separated list with no intervening spaces. are defined as follows: Hold cached attributes for no more than n seconds after directory update. The default value is Hold cached attributes for at least n seconds after directory update. The default value is Hold cached attributes for no more than n seconds after file modification. The default value is Hold cached attributes for at least n seconds after file modification. The default value is Set min and max times for regular files and directories to n seconds. has no default; it sets and to the value specified by n. If the first attempt fails, retry in the background or in the foreground The default is If is specified, then for the duration of the mount, forced direct is used. If the file system is mounted using data is trans- ferred directly between client and server, with no buffering on the client. If the file system is mounted using data is buffered on the client. is a performance option that is of benefit only in large sequential data transfers. The default behavior is By default, the GID associated with a newly created file obeys the System V semantics; that is, the GID is set to the effective GID of the calling process. This behavior can be overridden on a per-directory basis by setting the set-GID bit of the parent directory; in this case, the GID of a newly created file is set to the GID of the parent directory (see open(2) and mkdir(2)). Files cre- ated on file systems that are mounted with the option will obey BSD semantics independent of whether the set-GID bit of the parent directory is set; that is, the GID is unconditionally inherited from that of the parent directory. Continue to retry requests until the server responds or give up and return an error The default value is Allow or do not allow keyboard interrupts to kill a process that is hung while waiting for a response on a hard-mounted file system. The default is which allows clients to interrupt applications that can be waiting for a remote mount. By default, lock/unlock requests are sent to the server's which enforces the requests. With this option set, the lock/unlock requests are not sent to the remote and are enforced locally. These local locks are enforced much faster, but if other NFS clients access the same data on the server, there is a risk of data corruption. Consequently, this option must be used when only one NFS client accesses the data on the server. Suppress data and attribute caching. The data caching that is suppressed is the write-behind. The local page cache is still maintained, but data copied into it is immediately written to the server. Do not perform the normal close-to-open consistency. When a file is closed, all modified data associated with the file is flushed to the server and not held on the client. When a file is opened the client sends a request to the server to validate the client's local caches. This behavior ensures a file's consistency across multiple NFS clients. When is in effect, the client does not perform the flush on close and the request for validation, allowing the possibility of differences among copies of the same file as stored on multiple clients. This option can be used in situations that guarantee that accesses to a specified file system are made from only one client and only that client. Under such a condition, the effect of can be a slight performance gain. The server IP port number. The default is If the option is specified, and if the resource includes one or more NFS URLs, and if any of the include a num- ber, then the number in the option and in the URL must be the same. Request semantics for the file system. Requires a mount NFS Version 2 on the server. See mountd(1M). netid is a value of network_id field from entry in the file. By default, the transport protocol used for the NFS mount will be first available connection-oriented transport supported on both the client and the server. If no connection-oriented transport is found, then the first available connectionless transport is used. This default behavior can be overridden with the option. The option forces the use of the public file handle when connecting to the NFS server. The resource specified might not have an NFS URL. See the discussion on under for a more detailed discussion. Enable or prevent the command to check whether the user is over quota on this file system. If the file system has quotas enabled on the server, quotas are still checked for operations on this file system. See quota(1). Disable the functionality, which is used by default on an NFS Version 3 mount point, and use the NFS Version 2 functionality instead. The performance of applications that read huge directories over NFS will vary between NFS Version 2 and NFS Version 3 depending on the type of information that the applications need. The command will be faster using NFS Version 3 while the command will be faster using NFS Version 2 The option must be used on a case by case basis depending upon the application. There is no effect on an NFS Version 2 mount point. Remount a read-only file system as read-write (using the option). Set the number of NFS retransmissions to n. The default value is For connection-oriented transports, this option has no effect because it is assumed that the transport performs retransmissions on behalf of NFS. The number of times to retry the operation. The default for the command is resource is mounted read-write or read-only The default is Set the read buffer size to n bytes. The default value is when using Version 3 of the NFS protocol. The default can be negotiated down if the server prefers a smaller transfer size. When using Version 2, the default value is Set the security mode for NFS transactions. See nfssec(5) for the available security mode options. If is not specified, then the default action is to use over NFS Version 2 mounts, or to negotiate a security mode over NFS Ver- sion 3 mounts. NFS Version 3 mounts negotiate a security mode when the server returns an array of security modes. The client picks the first mode in the array that is supported on the client. Only one mode can be specified with the option. This option is equivalent to the option (Diffie-Hellman public key system). Setuid execution is allowed or disallowed The default is Set the NFS timeout to n tenths of a second. The default value is tenths of a second for connectionless transports, and tenths of a second for connection-oriented transports. By default, the version of NFS protocol used between the client and the server is the highest one available on both systems. If the NFS server does not support NFS Version 3 protocol, then the NFS mount will use NFS Version 2 protocol. To specify NFS Version 2, set NFS_version_number to be 2. To specify NFS Version 3, set NFS_version_number to be 3. If the option and are both specified, overrides the option. Set the write buffer size to n bytes. The default value is when using Version 3 of the NFS protocol. The default can be negotiated down if the server prefers a smaller transfer size. When using Version 2, the default value is Prevent printing a warning message for unknown specific_option. If the option is not specified, and an unknown specific_option is encountered, the utility prints a warning message and processes the next one. The option prevents printing the warning message. Overlay mount. Allow the file system to be mounted over an existing mount point, making the underlying file system inaccessible. If a mount is attempted on a pre-existing mount point without setting this flag, the mount will fail, producing the error Options (umount) The options are as follows: Attempt to unmount all NFS file systems described in Print debug messages to stderr. This option is to be used by HP support engineers. Forcibly unmount a file system. If this option is not specified, the utility does not allow a file system to be unmounted if a file on the file system is busy. Using the option can cause data loss for open files; programs which access files after the file system has been unmounted will get an error (EIO). NFS FILE SYSTEMS
Background versus Foreground File systems mounted with the option indicate that is to retry in the background if the server's mount daemon does not respond. See mountd(1M). retries the request up to the count specified in the option. Once the file system is mounted, each NFS request made in the kernel waits tenths of a second for a response. If no response arrives, the time-out is multiplied by and the request is retransmitted. When the number of retransmissions has reached the number specified in the option, a file system mounted with the option returns an error on the request; one mounted with the 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 option. Applications using mounted file systems can incur unexpected I/O errors, file corruption, unexpected program core dumps, and delays in system reboot/shutdown. The option is not recommended. Authenticated requests The server can require authenticated NFS requests from the client. The authentication (Diffie-Hellman public key system) might be required. See nfssec(5). URLs and the public Option If the option is specified, or if the resource includes an NFS URL, attempts to connect to the server using the public file handle lookup protocol. See If the server supports the public file handle, the attempt is successful; does not need to contact the server's and the dae- mons to get the port number of the server and the initial file handle of pathname, respectively. See rpcbind(1M) and mountd(1M). If the NFS client and server are separated by a firewall that allows all outbound connections through specific ports, such as then these ports enable NFS operations through the firewall. The option and the NFS URL can be specified independently or together. They interact as spec- ified in the following matrix: +--------------+-------------------------------------------+ | | Resource Style | | +---------------------+---------------------+ | | host:pathname | NFS URL | +--------------+---------------------+---------------------+ |public option | Force public file | Force public file | | | handle and fail | handle and fail | | | mount if not sup- | mount if not sup- | | | ported. Use Native | ported. Use Canon- | | | paths. | ical paths. | +--------------+---------------------+---------------------+ |Default | Use MOUNT protocol. | Try public file | | | | handle with Canoni- | | | | cal paths. Fall | | | | back to MOUNT pro- | | | | tocol if not sup- | | | | ported. | +--------------+---------------------+---------------------+ A Native path is a path name that is interpreted according to conventions used on the native operating system of the NFS server. A Canoni- cal path is a path name that is interpreted according to the URL rules. See See 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 contain equivalent directory structures and identical files. HP also recommends creating the file system directory structure with a utility such as (see rdist(1)). The file systems can be specified either with a comma-separated list of entries and/or NFS URL entries, or with a comma-separated list of hosts, if all file system 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, fails. Note that the option is always used for repli- cated servers. File Attributes To improve NFS read performance, files and file attributes are cached. File modification times get updated whenever a write occurs. How- ever, 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 modi- fied 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 sets flush time to n seconds for both regular files and directories. Setting disables attribute caching on the client. Then every reference to attributes is satisfied directly from the server though file data is still cached. Although the client is guaranteed to always have the latest file attributes from the server, performance is affected adversely through additional latency, network load, and server load. Setting the option also disables attribute caching, but has the further effect of disabling client write caching. Although this situation guarantees that an application can write data directly to a server so that the data can be viewed immediately by other clients, a signifi- cant adverse effect on client write performance can occur. Data written into memory-mapped file pages are not written directly to this server. See mmap(2). RETURN VALUE
returns the following values: Successful completion. An error occurred. See the section. ERRORS
If error code 157 is returned, has reached the process thread limit. Increase the value of nkthread. See nkthread(5) for more details. EXAMPLES
Example 1: Mounting an NFS File System To mount an NFS file system: Example 2: Mounting NFS File System Read-Only With No suid Privileges To mount an NFS file system read-only with no suid privileges: Example 3: Mounting NFS File System Over NFS Version 2 with the UDP Transport To mount an NFS file system over NFS Version 2 with the UDP transport: Example 4: Mounting NFS File System Using An NFS URL To mount an NFS file system using an NFS URL (a canonical path): Example 5: Mounting With Forcing Use Of The Public File Handle To mount an NFS file system and force the use of the public file handle and an NFS URL (a canonical path) that has a non 7-bit ASCII escape sequence: Example 6: Mounting an NFS File System Using a Native Path To mount an NFS file system using a native path (where the server uses colons as the component separator) and the public file handle: Example 7: Mounting a Replicated Set with Same Pathnames To mount a replicated set of NFS file systems with the same pathnames: Example 8: Mounting a Replicated Set with Different Pathnames To mount a replicated set of NFS file systems with different pathnames: WARNINGS
If the directory on which a file system is to be mounted is a symbolic link, the file system is mounted on the directory to which the sym- bolic link refers, rather than being mounted on top of the symbolic link itself. FILES
Table of mounted file systems Default distributed file system type Table of automatically mounted resources SEE ALSO
quota(1), rdist(1), fstyp(1M), lockd(1M), mountall(1M), mountd(1M), statd(1M), mkdir(2), mmap(2), mount(2), open(2), umount(2), mnttab(4), nfssec(5), quota(5), inet(7F), IPv6(7P). Callaghan, Brent, RFC 2054, October 1996. Callaghan, Brent, RFC 2224, October 1997. Berners-Lee, Masinter & McCahill , RFC 1738, December 1994. mount_nfs(1M)
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