mount_cachefs - mount CacheFS file systems
mount -F cachefs [ generic_options ] -o backfstype=file_system_type
[ other_cacheFS_options ] special_mount_point
The CacheFS-specific version of the mount command mounts a cached file
system; if necessary, it NFS-mounts its back file system. It also
provides a number of CacheFS-specific options for controlling the
To mount a CacheFS file system, use the generic mount command with the
-F option followed by the argument cachefs. The following generic
mount options are available:
-m Mount the file system without making an entry in the
-O Overlay mount. Allows the filesystem to be mounted
over an existing mount point, making the underlying
filesystem inaccessible. If a mount is attempted on a
pre-existing mount point without setting this flag,
mount will fail with the error:
mount -F cachefs: mount failed Device busy.
-r Mount the file system read-only.
The following arguments to the -o option are specifically for CacheFS
mounts. Use commas to separate multiple options. Note: the backfstype
argument must be specified.
The file system type of the back file system (for
backpath=path Specifies where the back file system is already
mounted. If this argument is not supplied, CacheFS
determines a mount point for the back file system. The
back file system must be read-only.
The name of the cache directory.
cacheid=ID ID is a string specifying a particular instance of a
cache. If you do not specify a cache ID, CacheFS will
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write-around | non-shared
Write modes for CacheFS. The write-around mode (the
default) handles writes the same as NFS does; that is,
writes are made to the back file system, and the
affected file is purged from the cache. You can use
the non-shared mode when you are sure that no one else
will be writing to the cached file system. In this
mode, all writes are made to both the front and the
back file system, and the file remains in the cache.
noconst Disables cache consistency checking. By default,
periodic consistency checking is enabled. Specify
noconst only when you know that the back file system
will not be modified. Trying to perform cache
consistency check using cfsadmin -s will result in
error. demandconst and noconst are mutually exclusive.
demandconst Verifies cache consistency only when explicitly
requested, rather than the periodic checking that is
done by default. A consistency check is requested by
using the -s option of the cfsadmin(1M) command. This
option is useful for back file systems that change
infrequently, for example, /usr/bin. demandconst and
noconst are mutually exclusive.
local-access Causes the front file system to interpret the mode bits
used for access checking instead or having the back
file system verify access permissions. Do not use this
argument with secure NFS .
purge Purge any cached information for the specified file
rw | ro Read-write (default) or read-only.
suid | nosuid Allow (default) or disallow set-uid execution.
acregmin=n Specifies that cached attributes are held for at least
n seconds after file modification. After n seconds,
CacheFS checks to see if the file modification time on
the back file system has changed. If it has, all
information about the file is purged from the cache and
new data is retrieved from the back file system. The
default value is 30 seconds.
acregmax=n Specifies that cached attributes are held for no more
than n seconds after file modification. After n
seconds, all file information is purged from the cache.
The default value is 30 seconds.
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acdirmin=n Specifies that cached attributes are held for at least
n seconds after directory update. After n seconds,
CacheFS checks to see if the directory modification
time on the back file system has changed. If it has,
all information about the directory is purged from the
cache and new data is retrieved from the back file
system. The default value is 30 seconds.
acdirmax=n Specifies that cached attributes are held for no more
than n seconds after directory update. After n
seconds, all directory information is purged from the
cache. The default value is 30 seconds.
actimeo=n Sets acregmin, acregmax, acdirmin, and acdirmax to n.
The following example CacheFS-mounts the file system server1:/user2,
which is already NFS-mounted on /usr/abc as /xyz.
example# mount -F cachefs -o backfstype=nfs,backpath=/usr/abc,
cachedir=/cache1 server1:/user2 /xyz
The lines similar to the following appear in the /etc/mnttab file
after the mount command is executed:
server1:/user2 /usr/abc nfs
/usr/abc /cache1/xyz cachefs backfstype=nfs
mount_cachefs was developed by Sun Microsystems, Inc.
cfsadmin(1M), fsck_cachefs(1M), mount(1M).
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