[archiso] Introduce cowfile_size= bootparam

If not set, nothing is changed in current behaviour.

Since dm-snapshot allows to use as "COW" a file with any size,
without caring about the the size of "origin", we can avoid creating a
"COW" file of the same size as the "origin". This is really useful,
when using as cow_device= a filesystem that is VFAT where sparse files
are not supported, so if root-image.fs is 1000M, passing cowfile_size=25%
will create a root-image.cow of 250M instead of 1000M.

Signed-off-by: Gerardo Exequiel Pozzi <vmlinuz386@yahoo.com.ar>

1 files changed, 5 insertions, 0 deletions

diff --git a/README b/README
index ce8d355..c33f444 100644
--- a/README
+++ b/README
@@ -65,6 +65,11 @@ INDEX
                     Size is in bytes (suffix with "k", "m" and "g") or
                     in percentage of available RAM.
                     Default: "75%"
+* cowfile_size=     Set the size for all files to be used as COW (dm-snapshot),
+                    in percentage of the ro-device.fs file. This is mostly useful
+                    when cow_device= is used and filesystem does not support
+                    sparse files (ie VFAT).
+                    Default: "100%"
 * copytoram_size=   Set the size of tmpfs. This space is used for
                     copy of all SquashFS images used, if copytoram=y.
                     Size is in bytes (suffix with "k", "m" and "g") or