1exportfs(8) System Manager's Manual exportfs(8)
2
6 exportfs - maintain table of exported NFS file systems
7
9 /usr/sbin/exportfs [-avi] [-o options,..] [client:/path ..]
10 /usr/sbin/exportfs -r [-v]
11 /usr/sbin/exportfs [-av] -u [client:/path ..]
12 /usr/sbin/exportfs [-v]
13 /usr/sbin/exportfs -f
14
16 An NFS server maintains a table of local physical file systems that are
17 accessible to NFS clients. Each file system in this table is referred
18 to as an exported file system, or export, for short.
19 The exportfs command maintains the current table of exports for the NFS
21 server. The master export table is kept in a file named
22 /var/lib/nfs/etab. This file is read by rpc.mountd when a client sends
23 an NFS MOUNT request.
24 Normally the master export table is initialized with the contents of
26 /etc/exports by invoking exportfs -a. However, a system administrator
27 can choose to add or delete exports without modifying /etc/exports by
28 using the exportfs command.
29 exportfs and its partner program rpc.mountd work in one of two modes: a
31 legacy mode which applies to 2.4 and earlier versions of the Linux ker‐
32 nel, and a new mode which applies to 2.6 and later versions, providing
33 the nfsd virtual filesystem has been mounted at /proc/fs/nfsd or
34 /proc/fs/nfs. On 2.6 kernels, if this filesystem is not mounted, the
35 legacy mode is used.
36 In the new mode, exportfs does not give any information to the kernel,
38 but provides it only to rpc.mountd through the /var/lib/nfs/etab file.
39 rpc.mountd then manages kernel requests for information about exports,
40 as needed.
41 In the legacy mode, exports which identify a specific host, rather than
43 a subnet or netgroup, are entered directly into the kernel's export ta‐
44 ble, as well as being written to /var/lib/nfs/etab. Further, exports
45 listed in /var/lib/nfs/rmtab which match a non host-specific export
46 request will cause an appropriate export entry for the host given in
47 rmtab to be added to the kernel's export table.
48
50 -a Export or unexport all directories.
51 -o options,...
53 Specify a list of export options in the same manner as in
54 exports(5).
55 -i Ignore the /etc/exports file. Only default options and options
57 given on the command line are used.
58 -r Reexport all directories, synchronizing /var/lib/nfs/etab with
60 /etc/exports. This option removes entries in /var/lib/nfs/etab
61 which have been deleted from /etc/exports, and removes any
62 entries from the kernel export table which are no longer valid.
63 -u Unexport one or more directories.
65 -f If /proc/fs/nfsd or /proc/fs/nfs is mounted, flush everything
67 out of the kernel's export table. Fresh entries for active
68 clients are added to the kernel's export table by rpc.mountd
69 when they make their next NFS mount request.
70 -v Be verbose. When exporting or unexporting, show what's going on.
72 When displaying the current export list, also display the list
73 of export options.
74
76 Exporting Directories
77 The first synopsis shows how to invoke exportfs when adding new entries
78 to the export table. When using exportfs -a, all exports listed in
79 /etc/exports are added to /var/lib/nfs/etab. The kernel's export table
80 is also updated as needed.
81 The host:/path argument specifies a local directory to export, along
83 with the client or clients who are permitted to access it. See
84 exports(5) for a description of supported options and access list for‐
85 mats. To export a directory to the world, simply specify :/path.
86 The export options for a particular host/directory pair derive from
88 several sources. The default export options are
89 sync,ro,root_squash,wdelay. These can be overridden by entries in
90 /etc/exports.
91 A system administrator may override options from these sources using
93 the -o command-line option on exportfs. This option takes a comma-sep‐
94 arated list of options in the same fashion as one would specify them in
95 /etc/exports. In this way exportfs can be used to modify the export
96 options of an already exported directory.
97 Unexporting Directories
99 The third synopsis shows how to unexported a currently exported direc‐
100 tory. When using exportfs -ua, all entries listed in /var/lib/nfs/etab
101 are removed from the kernel export tables, and the file is cleared.
102 This effectively shuts down all NFS activity.
103 To remove an export, specify a host:/path pair. This deletes the speci‐
105 fied entry from /var/lib/nfs/etab and removes the corresponding kernel
106 entry (if any).
107 Dumping the Export Table
109 Invoking exportfs without options shows the current list of exported
110 file systems. Adding the -v option causes exportfs to display the
111 export options for each export.
112
114 The following adds all directories listed in /etc/exports to
115 /var/lib/nfs/etab and pushes the resulting export entries into the ker‐
116 nel:
117 # exportfs -a
119 To export the /usr/tmp directory to host django, allowing insecure file
121 locking requests from clients:
122 # exportfs -o insecure_locks django:/usr/tmp
124 To unexport the /usr/tmp directory:
126 # exportfs -u django:/usr/tmp
128 To unexport all exports listed in /etc/exports:
130 # exportfs -au
132
134 Exporting to IP networks or DNS and NIS domains does not enable clients
135 from these groups to access NFS immediately. Rather, these sorts of
136 exports are hints to rpc.mountd(8) to grant any mount requests from
137 these clients. This is usually not a problem, because any existing
138 mounts are preserved in rmtab across reboots.
139 When unexporting a network or domain entry, any current exports to mem‐
141 bers of this group will be checked against the remaining valid exports
142 and if they themselves are no longer valid they will be removed.
143
145 /etc/exports input file listing exports, export options,
146 and access control lists
147 /var/lib/nfs/etab master table of exports
149 /var/lib/nfs/rmtab table of clients accessing server's exports
151
153 exports(5), rpc.mountd(8), netgroup(5)
154
156 Olaf Kirch <okir@monad.swb.de>
157 Neil Brown <neilb@cse.unsw.edu.au>
158 31 December 2009 exportfs(8)