Subject: Behavier of mount_union with writable on read-only
To: None <>
From: MASUDA Hideo <>
List: tech-kern
Date: 03/13/2006 17:09:17
Hi, all.

 I want to make writable directories/files on read-only directories/files
such as cd9660.
 For this, mount_union may be useful.

 I have tried as following:

# mount -t cd9660 -o ro /dev/cd0a /
# mount -t mfs -o -s=10240 none /.var
# mount -t union /.var /var
# rm /var/log/messages
override rw-r--r--  root/wheel for '/var/log/messages'? yes  <--(*1)
# ls /var/log/messages
ls: /var/log/messages: No such file or directory

 /var/log/messages can be deleted with union behavior, but (*1) is
also happened. This causes that syslogd can not write log messages.
 Can I suppress/change the (*1) behavior in union'ed directory ?

Thank you in advance.