rmtab.5nfs

来自「<B>Digital的Unix操作系统VAX 4.2源码</B>」· 5NFS 代码 · 共 81 行

.\" SCCSID: @(#)rmtab.5nfs	8.1	9/11/90
.TH rmtab 5nfs
.SH Name
rmtab \- table of local file systems mounted by remote NFS clients
.SH Description
.NXR "rmtab file"
.NXR "NFS protocols" "remote hosts and"
.NXAM "showmount command" "rmtab file"
.NXAM "mount command (NFS)" "rmtab file"
The
.PN rmtab
file resides in the 
.PN /etc
directory and contains a list of all remote hosts that have mounted
local file systems using the NFS protocols.
Whenever a client performs a remote mount,
the server machine's mount daemon
makes an entry in the server machine's
.PN rmtab
file.
The 
.PN umount
command instructs the server's mount daemon to remove the entry.
The 
.PN nfs_umount 
.B \-b
command broadcasts to all servers 
and informs them that they should remove
all entries from
.PN rmtab
created by the sender of the broadcast message.
By placing a 
.PN nfs_umount 
.B \-b
command in 
.PN /etc/rc.local ,
.PN rmtab
tables on NFS servers can be purged of entries made by a crashed
client, who, upon rebooting, did not remount the same file systems that
it had before the system crashed.  The 
.PN rmtab 
file is a series of lines of the form:
.EX
hostname:directory
.EE
.PP
Rather than rewrite the rmtab file on each
.PN umount
request, the mount daemon comments out unmounted entries by placing a
number sign (#) in the first character position of the appropriate line.
The mount daemon rewrites the entire file, without commented out 
entries, no more frequently than every 30 minutes.  The frequency
depends on the occurrence of
.PN umount
requests.
.PP
This table is used only to preserve information between crashes
and is read only by
.MS mountd 8nfs
when it starts up.
The 
.PN mountd
daemon keeps an in-core table,
which it uses to handle requests from programs like
.MS showmount 8nfs
and
.MS shutdown 8 .
.SH Restrictions
Although the
.PN rmtab
table is close to the truth,
it may contain erroneous information if
NFS client machines fail to execute
.PN umount 
.B \-a 
when they reboot.
.SH Files
.PN /etc/rmtab
.SH See Also
mount(8nfs), umount(8nfs), mountd(8nfs), showmount(8nfs), shutdown(8)