modprobe cowloop [maxcows=...] [rdofile=... cowfile=... [option=r]]
takes care that the cowloop driver is loaded into the kernel.
maxcows= can be used
to specify how many cowdevices should be supported in
parallel. The default value is 16, accessible via the cowdevices
The current maximum value is 254.
Version 3.3. will increase the maximum to 1022.
(more info on how to modify this
maximum is in the file
It is possible to activate the first cowdevice
already while loading the cowloop driver:
The pathname of the read-only file or filesystem.
The read-only file(system) may be of type regular or block-device.
The pathname of the copy-on-write file used as
storage-space for modified blocks of the read-only file(system).
The copy-on-write file is always a regular file.
If the given copy-on-write file does not yet exist, a new file
with this name will be created by the cowloop driver.
If an existing regular file is specified as cowfile,
its contents will be used again for the current read-only file
(the cowfile is supposed to contain modified blocks from an earlier
session for the same read-only file).
Notice that an existing cowfile must be in a consistent state.
This means that the previous session should have been finished
properly by deactivating the cowdevice via the command
or by unloading the cowloop driver
When the cowfile has not been properly closed, the cowloop driver
refuses to assign it again unless the parameter
option=r is given with the command
This option forces that the cowfile is repaired automatically if it
appears to be inconsistent.
In that case the command
modprobe might take some time!
Notice that this option should only be used for special purposes.
Inconsistent cowfiles should preferably be repaired with the command
before activating the cowdevice.
When failures occur during driver-loading, more information about the
reason of the failure can be found in the
takes care that the cowloop driver is unloaded again (all active
cowdevices will be deactivated automatically).