mount_mfs
—
mount a memory based file system
mount_mfs |
[-N ] [-a
maxcontig] [-b
block-size] [-d
rotdelay] [-e
maxbpg] [-f
frag-size] [-g
groupname] [-i
bytes-per-inode] [-m
free-space] [-n
inodes] [-o
options] [-p
permissions] [-s
size] [-u
username] [-V
verbose] special node |
mount_mfs
is used to build a file system in virtual
memory and then mount it on a specified node.
mount_mfs
exits and the contents of the file system
are lost when the file system is unmounted. If
mount_mfs
is sent a signal while running, for example
during system shutdown, it will attempt to unmount its corresponding file
system. special is ignored.
Options with numeric arguments may contain an optional
(case-insensitive) suffix:
- b
- Bytes; causes no modification. (Default)
- k
- Kilo; multiply the argument by 1024
- m
- Mega; multiply the argument by 1048576
- g
- Giga; multiply the argument by 1073741824
The following options define the general layout policies:
-N
- Causes the memory file system parameters to be printed out without really
mounting the memory file system.
-a
maxcontig
- This specifies the maximum number of contiguous blocks that will be laid
out before forcing a rotational delay (see the
-d
option). The default value is 8. See
tunefs(8) for more details
on how to set this option.
-b
block-size
- The block size of the file system, in bytes. It must be a power of two.
The smallest allowable size is 4096 bytes. The default size depends upon
the size of the file system:
- file system size
- block-size
- < 20 MB
- 4 KB
- < 1024 MB
- 8 KB
- >= 1024 MB
- 16 KB
-d
rotdelay
- This specifies the expected time (in milliseconds) to service a transfer
completion interrupt and initiate a new transfer on the same disk. The
default is 0 milliseconds. See
tunefs(8) for more details
on how to set this option.
-e
maxbpg
- This indicates the maximum number of blocks any single file can allocate
out of a cylinder group before it is forced to begin allocating blocks
from another cylinder group. The default is about one quarter of the total
blocks in a cylinder group. See
tunefs(8) for more details
on how to set this option.
-f
frag-size
- The fragment size of the file system in bytes. It must be a power of two
ranging in value between block-size/8 and
block-size. The optimal
block-size:frag-size ratio is
8:1. Other ratios are possible, but are not recommended, and may produce
unpredictable results. The default size depends upon the size of the file
system:
- file system size
- frag-size
- < 20 MB
- 0.5 KB
- < 1024 MB
- 1 KB
- >= 1024 MB
- 2 KB
-g
groupname
- This specifies the group name or group id of the root inode of the file
system.
-i
bytes-per-inode
- This specifies the density of inodes in the file system. If fewer inodes
are desired, a larger number should be used; to create more inodes a
smaller number should be given. The default is to create an inode for
every (4 * frag-size) bytes of data space:
- file system size
- bytes-per-inode
- < 20 MB
- 2 KB
- < 1024 MB
- 4 KB
- >= 1024 MB
- 8 KB
-m
free-space
- The percentage of space reserved from normal users; the minimum free space
threshold. The default value used is 5%. See
tunefs(8) for more details
on how to set this option.
-n
inodes
- This specifies the number of inodes for the filesystem. If both
-i
and -n
are specified
then -n
takes precedence.
-o
- Options are specified with a
-o
flag followed by a
comma separated string of options. See the
mount(8) man page for
possible options and their meanings.
-p
permissions
- This specifies the permissions of the root inode of the file system.
-s
size
- The size of the file system in sectors. An ‘s’ suffix will
be interpreted as the number of sectors (the default). All other suffixes
are interpreted as per other numeric arguments, except that the number is
converted into sectors by dividing by the default sector size (which is
512 bytes) after suffix interpretation.
-u
username
- This specifies the user name or user id of the root inode of the file
system.
-V
verbose
- This controls the amount of information written to stdout:
- 0
- No output
- 1
- Overall size and cylinder group details.
- 2
- A progress bar (dots ending at right hand margin).
- 3
- The first few super-block backup sector numbers are displayed before
the progress bar.
- 4
- All the super-block backup sector numbers are displayed (no progress
bar).
The default is 0. If -N
is specified
mount_mfs
stops before outputting the progress
bar.
The owner and group ids of the root node of the new file system are set to the
effective uid and gid of the user mounting the file system.
Mount a 32 MB mfs on /tmp:
mount_mfs -s 32m swap
/tmp
disktab(5),
fs(5),
disklabel(8),
diskpart(8),
dumpfs(8),
fsck_ffs(8),
fsirand(8),
mount(8),
newfs(8),
tunefs(8)
M. McKusick,
W. Joy, S. Leffler, and
R. Fabry, A Fast File System for
UNIX,, ACM Transactions on Computer Systems 2,
3, pp 181-197,
August 1984, (reprinted in the
BSD System Manager's Manual).
The mount_mfs
command appeared in
4.4BSD.
The async
mount(8) option is currently
disabled in this file system because it causes hangs when writing lots of
data. The problem is that MFS needs to allocate pages to clean pages, so if it
waits until the last minute to clean pages then there may not be any of them
available to do the cleaning.