MOUNTCTL(8) BSD System Manager's Manual MOUNTCTL(8)NAMEmountctl — control journaling and other features on mounted file systems
SYNOPSISmountctl-l {mountpt | tag | mountpt:tag}
mountctl-a [-2] [-w/W output_path] [-x/X filedesc] [-o options]
mountpt:tag
mountctl-r [-2] [-w/W output_path] [-x/X filedesc] mountpt:tag
mountctl-d {mountpt | tag | mountpt:tag}
mountctl-m [-o options] {mountpt | tag | mountpt:tag}
mountctl-FZSCA {mountpt | tag | mountpt:tag}
DESCRIPTION
The mountctl utility manages journaling and (eventually) other features
on a mounted filesystem. Note that a mount point path must begin with
‘/’, and tag names must not begin with ‘/’.
mountctl-l will list all installed journals in the system or on a par‐
ticular mount point or tag, including their current state of operation.
mountctl-a will add a new journal to a mount point. A mount may have
any number of journals associated with it. If no output path is speci‐
fied the journal will be written to the standard output. Options may be
specified as described in the OPTION KEYWORDS section. The tag is
required and must be unique relative to any given mount, but you can use
the same tag on multiple mount points if you wish (and control them all
together by referencing that tag). The output path may represent any
streamable entity. You can, for example, output to a pipe into a program
which does further buffering or processing of the journal. WARNING A
stalled journaling descriptor will stall the filesystem. Eventually a
kernel-implemented swap backing will be available for journals but that
is not the case at the moment.
mountctl-r will restart an existing journal, directing it to a new file
descriptor. A shutdown is sent to the old journal and the system waits
for the return direction (if running full-duplex) to EOF. The new
descriptor is then installed and the FIFO index is reset to the last
acknowledged transaction. Clients scanning a journal across such a dis‐
connect must check for repeated transaction ids since some overlap
between the old and new journal may occur.
mountctl-d will remove the specified journal(s). A mount point, a tag,
or both may be specified. This function will operate on all matching
journals.
mountctl-m will modify the options associated with an existing journal.
Options are specified in the OPTION KEYWORDS section.
OTHER OPTIONS-2 Specify full-duplex operation. The kernel will not throw away
journal data in its internal FIFO until the transaction id is
acknowledged. This requires a full-duplex journaling descriptor.
Note that shell pipes are full-duplex-capable.
-F Flush a journal, equivalent to the flush keyword. This option
implies -m.
-Z Freeze a journal, equivalent to the freeze keyword. This option
implies -m if -a or -d are not specified.
-S Start a stopped journal, equivalent to the start keyword. This
option implies -m.
-C Close a journal, equivalent to the close keyword. This option
implies -m.
-A Abort a journal, equivalent to the abort keyword. This option
implies -m.
-w output_path
Change a journal's stream descriptor to the specified path. This
option implies -m if -a or -d are not specified. The target file
must not reside on the same filesystem being journaled.
-W output_path
Same as -w but overrides target safety checks.
-x filedesc
Change a journal's stream descriptor to the specified file
descriptor number. This option implies -m if -a or -d are not
specified. The target file must not reside on the same filesys‐
tem being journaled.
-X filedesc
Same as -x but overrides target safety checks.
-o options
Specify options, see OPTION KEYWORDS.
OPTION KEYWORDS
Options keywords may be comma delimited without whitespace within a sin‐
gle -o or via multiple -o options. Some keywords require a value which
is specified as keyword=value. Any option may be prefixed with ‘no’ or
‘non’ to turn off the option. Some options are one-shot and have no ‘no’
or ‘non’ equivalent.
The options are as follows:
reversable
Generate a reversable journaling stream. This allows the target
to run the journal backwards as well as forwards to ‘undo’ opera‐
tions. This is the default.
twoway Indicate that the journaling stream is a two-way stream and that
transaction id acknowledgements will be returned. This option is
the same as the -2 option.
memfifo=size[k,m]
Specify the size of the in-kernel memory FIFO used to buffer the
journaling stream between processes doing filesystem operations
and the worker thread writing out the journal. Since the kernel
has limited virtual memory buffers larger than 4MB are not recom‐
mended.
swapfifo=size[k,m,g]
Specify the size of the kernel-managed swap-backed FIFO used to
buffer overflows.
path=filepath
Specify where the journal's output stream should be directed.
Note that the -w option is equivalent to specifying the path
option. Both should not be specified.
fd=filedesc
Specify where the journal's output stream should be directed by
handing over a file descriptor. Use file descriptor 1 if you
wish to output the journal to the current stdout. Note that the
-w option is equivalent to specifying the path option. Both
should not be specified.
freeze Freeze the worker thread. This may cause the filesystem to stall
once the memory fifo has filled up. A freeze point record will
be written to the journal. If used as part of the creation of a
new journal via -a, this option will prevent any initial output
to the journal and a freeze point record will NOT be written.
Again, the filesystem will stall if the memory fifo fills up.
start Start or restart the worker thread after a freeze.
close Close the journal. Any transactions still under way will be
allowed to complete, a closing record will be generated, and the
journaling descriptor will be closed. If the connection is two-
way the journal will away a final acknowledgement of the closing
record before closing the descriptor.
abort Close the journal. Any currently buffered data will be aborted.
No close record is written. The journaling stream is immediately
closed.
flush Flush the journal. All currently buffered data is flushed. The
command does not return until the write succeeds and, if the con‐
nection is two-way, and acknowledgement has been returned for
journaled data buffered at the time the flush was issued.
SEE ALSOmount(2), mountctl(2), jscan(8)CAVEATS
This utility is currently under construction and not all features have
been implemented yet. In fact, most have not.
HISTORY
The mountctl utility first appeared in DragonFly 1.2.
BSD September 28, 2009 BSD
