====== How to Configure and Use the Read-Only and Read-Write Directories Feature ======

One of the significant differences between Debian Linux and Voyage Linux is the support for using Compact Flash instead of a hard drive.

The way this works in Voyage is that the flash 'disk' is very rarely written to, to avoid wear.
Most of the filesystem is normally in Read-Only (RO) mode. 

By default, **you can't write to most directories, ** except for /var/log and /var/tmp

If you need some directories to be writeable and optionally persist through a restart, these directories have to be configured.

However, if your system has got a hard drive, you can disable this RO/RW feature, by commenting out line 79 (approximately) in /etc/init.d/voyage-util:
<code>/usr/local/sbin/remountro</code>
becomes
<code>#/usr/local/sbin/remountrw</code>
as explained in [[remove_ro]]



====== Configuration of Writeable Directories ======
To make some other directories writeable, edit /etc/default/voyage-util.
At the line
<code>VOYAGE_SYNC_DIRS=""</code>
insert a space separated list of directories between the quotation marks. For example, to add /var/mail and /home/someone, change this line to
<code>VOYAGE_SYNC_DIRS="/var/mail /home/someone"</code>

The way this works is that /etc/init.d/voyage-sync creates an overlay over the selected directories, using the tmpfs filesystem, which runs in RAM. Any changes made are written to the RAM-based overlay. If the power fails, the changes are lost.

By editing /etc/default/voyage-util at the line 
''VOYAGE_UNIONFS=""'', you can change to using unionfs or aufs instead of tmpfs, but the operation remains the same.

**Caution:** Don't put **/etc** in the list of directories to be writeable. There is a problem during shutdown, as some files are busy and cannot be synchronised.


====== To make writeable directories persist through a restart ======
The writeable directories do **not** necessarily persist through a restart. Any information written will be lost.

However, you can periodically take a snapshot of their modified state by running these commands as the root user:
<code>
remountrw
/etc/init.d/voyage-sync sync
remountro
</code>

This takes a copy of the modified state of the writeable directories, and saves it in /.sync

It does **not** save it to the proper location, at least not yet.

They are saved to their proper original locations on a shutdown.



====== What if the power fails before a shutdown? ======
Before voyage 0.6.5, if the power failed before a normal shutdown, the snapshot information was lost.

From voyage 0.6.5:
"The issue with data loss from /.sync/xxx when a power-loss occures is 'fixed'. You can sync with 'voyage-sync sync' as often as you wish and data from last sync is recovered at reboot. Please take a look into '/etc/default/voyage-util' " [0.6.5 README]

__Rodney, Apr 2010__

To make it really work you have to edit /etc/default/voyage-util.
At the line
<code>
# set it to YES to enable recovery of directories after a power failure
VOYAGE_SYNC_RECOVER="YES"
</code>