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 /usr/sbin/exportfs -s
15
17 An NFS server maintains a table of local physical file systems that are
18 accessible to NFS clients. Each file system in this table is referred
19 to as an exported file system, or export, for short.
20 The exportfs command maintains the current table of exports for the NFS
22 server. The master export table is kept in a file named
23 /var/lib/nfs/etab. This file is read by rpc.mountd when a client sends
24 an NFS MOUNT request.
25 Normally the master export table is initialized with the contents of
27 /etc/exports and files under /etc/exports.d by invoking exportfs -a.
28 However, a system administrator can choose to add or delete exports
29 without modifying /etc/exports or files under /etc/exports.d by using
30 the exportfs command.
31 exportfs and its partner program rpc.mountd work in one of two modes: a
33 legacy mode which applies to 2.4 and earlier versions of the Linux ker‐
34 nel, and a new mode which applies to 2.6 and later versions, providing
35 the nfsd virtual filesystem has been mounted at /proc/fs/nfsd or
36 /proc/fs/nfs. On 2.6 kernels, if this filesystem is not mounted, the
37 legacy mode is used.
38 In the new mode, exportfs does not give any information to the kernel,
40 but provides it only to rpc.mountd through the /var/lib/nfs/etab file.
41 rpc.mountd then manages kernel requests for information about exports,
42 as needed.
43 In the legacy mode, exports which identify a specific host, rather than
45 a subnet or netgroup, are entered directly into the kernel's export ta‐
46 ble, as well as being written to /var/lib/nfs/etab. Further, exports
47 listed in /var/lib/nfs/rmtab which match a non host-specific export
48 request will cause an appropriate export entry for the host given in
49 rmtab to be added to the kernel's export table.
50
52 -d kind or --debug kind
53 Turn on debugging. Valid kinds are: all, auth, call, general and
54 parse. Debugging can also be turned on by setting debug= in the
55 [exportfs] section of /etc/nfs.conf.
56 -a Export or unexport all directories.
59 -o options,...
61 Specify a list of export options in the same manner as in
62 exports(5).
63 -i Ignore the /etc/exports file and files under /etc/exports.d
65 directory. Only default options and options given on the com‐
66 mand line are used.
67 -r Reexport all directories, synchronizing /var/lib/nfs/etab with
69 /etc/exports and files under /etc/exports.d. This option
70 removes entries in /var/lib/nfs/etab which have been deleted
71 from /etc/exports or files under /etc/exports.d, and removes any
72 entries from the kernel export table which are no longer valid.
73 -u Unexport one or more directories.
75 -f If /proc/fs/nfsd or /proc/fs/nfs is mounted, flush everything
77 out of the kernel's export table. Fresh entries for active
78 clients are added to the kernel's export table by rpc.mountd
79 when they make their next NFS mount request.
80 -v Be verbose. When exporting or unexporting, show what's going on.
82 When displaying the current export list, also display the list
83 of export options.
84 -s Display the current export list suitable for /etc/exports.
86
88 Exporting Directories
89 The first synopsis shows how to invoke exportfs when adding new entries
90 to the export table. When using exportfs -a, all exports listed in
91 /etc/exports and files under /etc/exports.d are added to
92 /var/lib/nfs/etab. The kernel's export table is also updated as
93 needed.
94 The host:/path argument specifies a local directory to export, along
96 with the client or clients who are permitted to access it. See
97 exports(5) for a description of supported options and access list for‐
98 mats.
99 IPv6 presentation addresses contain colons, which are already used to
101 separate the "host" and "path" command line arguments. When specifying
102 a client using a raw IPv6 address, enclose the address in square brack‐
103 ets. For IPv6 network addresses, place the prefix just after the clos‐
104 ing bracket.
105 To export a directory to the world, simply specify :/path.
107 The export options for a particular host/directory pair derive from
109 several sources. The default export options are
110 sync,ro,root_squash,wdelay. These can be overridden by entries in
111 /etc/exports or files under /etc/exports.d.
112 A system administrator may override options from these sources using
114 the -o command-line option on exportfs. This option takes a comma-sep‐
115 arated list of options in the same fashion as one would specify them in
116 /etc/exports. In this way exportfs can be used to modify the export
117 options of an already exported directory.
118 Unexporting Directories
120 The third synopsis shows how to unexport a currently exported direc‐
121 tory. When using exportfs -ua, all entries listed in /var/lib/nfs/etab
122 are removed from the kernel export tables, and the file is cleared.
123 This effectively shuts down all NFS activity.
124 To remove an export, specify a host:/path pair. This deletes the speci‐
126 fied entry from /var/lib/nfs/etab and removes the corresponding kernel
127 entry (if any).
128 Dumping the Export Table
130 Invoking exportfs without options shows the current list of exported
131 file systems. Adding the -v option causes exportfs to display the
132 export options for each export.
133
135 The following adds all directories listed in /etc/exports and files
136 under /etc/exports.d to /var/lib/nfs/etab and pushes the resulting
137 export entries into the kernel:
138 # exportfs -a
140 To export the /usr/tmp directory to host django, allowing insecure file
142 locking requests from clients:
143 # exportfs -o insecure_locks django:/usr/tmp
145 To unexport the /usr/tmp directory:
147 # exportfs -u django:/usr/tmp
149 To unexport all exports listed in /etc/exports and files under
151 /etc/exports.d:
152 # exportfs -au
154 To export the /usr/tmp directory to IPv6 link-local clients:
156 # exportfs [fe80::]/64:/usr/tmp
158
160 Exporting to IP networks or DNS and NIS domains does not enable clients
161 from these groups to access NFS immediately. Rather, these sorts of
162 exports are hints to rpc.mountd(8) to grant any mount requests from
163 these clients. This is usually not a problem, because any existing
164 mounts are preserved in rmtab across reboots.
165 When unexporting a network or domain entry, any current exports to mem‐
167 bers of this group will be checked against the remaining valid exports
168 and if they themselves are no longer valid they will be removed.
169
171 /etc/exports input file listing exports, export options,
172 and access control lists
173 /etc/exports.d directory where extra input files are stored.
175 Note: only files that end with .exports are
176 used.
177 /var/lib/nfs/etab master table of exports
179 /var/lib/nfs/rmtab table of clients accessing server's exports
181
183 exports(5), nfs.conf(5), rpc.mountd(8), netgroup(5)
184
186 Olaf Kirch <okir@monad.swb.de>
187 Neil Brown <neilb@cse.unsw.edu.au>
188 30 September 2013 exportfs(8)