mountdtab - Table of local file systems mounted by remote
NFS clients
/etc/mountdtab
The mountdtab file resides in the /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 mountdtab file.
The umount command instructs the server's mount daemon to
remove the entry. The umount -b command broadcasts to all
servers and informs them that they should remove all
entries from mountdtab created by the sender of the broadcast
message. By placing an umount -b command in a system
startup file, mountdtab 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. Tru64 UNIX systems automatically
call umount -b at system startup
The format for entries in the mountdtab file is as follows:
hostname:directory Rather than rewrite the mountdtab
file on each 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 umount
requests.
The mountdtab table is used only to preserve information
between crashes and is read only by the mountd daemon when
it starts up. The mountd daemon keeps an in-core table,
which it uses to handle requests from programs like showmount
and shutdown.
Although the mountdtab table is close to the truth, it may
contain erroneous information if NFS client machines fail
to execute a umount -a command when they reboot.
mount(8), umount(8), mountd(8), showmount(8), shutdown(8)
delim off
mountdtab(4)
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