To solve these kinds of problems, carefully watch the console of
a booting node for errors related to a 'Read-only file system'. When
these kinds of errors occur, determine which file or directory was
trying to be written to and
include LINKDIR or LINKFILE directives in the configuration as appropriate.
As an example, several distributions like to write .pid files into /var/run to keep track of the process IDs of running daemons. At boot time, when these daemons try to start, there will be complaints about a 'Read-only file system' when /var/run is not writable. One solution for this problem is to add the following directive to the sysimage.conf file of the master image:
Giving a daemon the ability to write to a single file, such as /var/lib/random-seed, can be handled similarly. Rather than link all of /var/lib into the RAM disk, link just the needed file:
Closely watch the bootup and add any needed directives to the configuration to handle the idiosyncrasies of a read-only root filesystem. On a side note, it also helps to disable most of the unnecessary daemons enabled by default in many distributions.