System information

By default, access control lists (ACLs) are supported by NFS under Red Hat Enterprise Linux. To
disable this feature, specify the no _acl option when exporting the file system.
Each default for every exported file system must be explicitly overridden. For example, if the rw option
is not specified, then the exported file system is shared as read-only. The following is a sample line
from /etc/expo rts which overrides two default options:
/ano ther/expo rted /d i recto ry 19 2. 16 8. 0 . 3(rw,async)
In this example 19 2. 16 8. 0 . 3 can mount /ano ther/expo rted /d i recto ry/ read/write and all
writes to disk are asynchronous. For more information on exporting options, refer to man expo rtfs.
Other options are available where no default value is specified. These include the ability to disable
sub-tree checking, allow access from insecure ports, and allow insecure file locks (necessary for
certain early NFS client implementations). Refer to man expo rts for details on these less-used
options.
Important
The format of the /etc/expo rts file is very precise, particularly in regards to use of the space
character. Remember to always separate exported file systems from hosts and hosts from one
another with a space character. However, there should be no other space characters in the file
except on comment lines.
For example, the following two lines do not mean the same thing:
/home bob.example.com(rw)
/home bob.example.com (rw)
The first line allows only users from bo b. exampl e. co m read/write access to the /ho me
directory. The second line allows users from bo b. exampl e. co m to mount the directory as
read-only (the default), while the rest of the world can mount it read/write.
9.7.2. T he expo rtfs Command
Every file system being exported to remote users with NFS, as well as the access level for those file
systems, are listed in the /etc/expo rts file. When the nfs service starts, the
/usr/sbi n/expo rtfs command launches and reads this file, passes control to rpc. mo untd (if
NFSv2 or NFSv3) for the actual mounting process, then to rpc. nfsd where the file systems are then
available to remote users.
When issued manually, the /usr/sbi n/expo rtfs command allows the root user to selectively
export or unexport directories without restarting the NFS service. When given the proper options, the
/usr/sbi n/expo rtfs command writes the exported file systems to /var/l i b/nfs/etab. Since
rpc. mo untd refers to the etab file when deciding access privileges to a file system, changes to the
list of exported file systems take effect immediately.
The following is a list of commonly-used options available for /usr/sbi n/expo rtfs:
- r
⁠Chapt er 9 . Net work File Syst em (NFS)
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