Hi. I checked around a lot to see if any advancements have been made in 
mounting / read-only, and it doesn't look like it. I found 3 methods:

Symlink /etc/mtab to /proc/mounts. The downside to this is that loopback 
mounts don't show up, and so umount doesn't take down the loop device.

Symlink /etc/mtab to a real file, like /var/lib/mtab. The readonly_rootfs.txt 
suggested hard coding the new file in Glibc and Util-linux.

Third is mounting /etc as it's own partition. See:
http://www.seifried.org/oag/advanced-filesystem/
I like this one best, personally, because it makes it easy to reuse /etc when 
upgrading (if all config's are put there), and because /etc can be read-write 
while / is read-only. I have two / and two /usr partitions, so I can upgrade 
to a scratch system, so reusing an /etc partition (along with /boot 
and /home) would be nice. This also allows /etc to be mounted, to change 
passwords or whatever, without mounting /. The downside to this is /etc/fstab 
exists twice (one on /, another on /etc, partitions), and need to both be 
valid, and there's still an issue with /etc/mtab.

/etc/resolv.conf might also need a symlink to /somewhere/resolv.conf, 
depending on whether you change this file during uptime.

Any other ideas?

Also, for the above reason and more, I'm always looking for better ways to 
partition. This is my latest idea (with 3 drives), for a desktop:

devpts on /dev/pts type devpts (rw,nosuid,gid=4,mode=620)
shm on /dev/shm type tmpfs (rw,nosuid,nodev,mode=1777)
tmpfs on /tmp type tmpfs (rw,nosuid,nodev,size=512m,mode=1777)
Symlink /var/tmp to /tmp

ide 80G. These partitions get reused with dual-boots:
        extended                80G
        /boot           2G              ro,noexec,nosuid,nodev                  
        ext3
        /etc                    512M    ro,noexec,nosuid,nodev                  
        ext3
        /root                   4G              rw,noexec,nosuid,nodev          
                ext3
        /var                    4G              rw,nosuid,nodev                 
                ext3
        /var/spool      4G              rw,noexec,nosuid,nodev,noatime,sync     
ext2    AES128
        /multimedia     -               rw,noexec,nosuid,nodev,noatime,sync     
ext2    AES128

Note: As per the loop-aes README file, if a journaling file system is used 
then write cache should be disabled on the drive to allow the file system to 
handle all the writes. For this drive I prefer to leave write caching enabled 
and use ext2 with the sync option, which is only sane with the noatime 
option. On a server, something like the Mars or Twofish algorithm might be a 
better idea for performance, but requires additional kernel modules to be 
loaded.

Symlink /etc/resolv.conf to /tmp/resolv.conf
Symlink /etc/mtab to /tmp/mtab
Symlink /var/log to /var/spool/log
Symlink /var/mail to /var/spool/mail

sata 250G (write caching disabled via `hdparm` in bootscript):
        /home           -               rw,nosuid,nodev,noatime                 
ext3    AES256

sata 80G:
         extended       80G
        swap            4G                                                      
                                AES128
        /                       2G              ro,nodev                        
                                ext3
        /usr                    12G             ro,nodev                        
                                ext3
        /                       2G              ro,nodev                        
                                ext3
        /usr                    12G             ro,nodev                        
                                ext3
        /usr/src                -               rw,noexec,nosuid,nodev,noatime  
        ext3

Symlink /opt to /usr/opt.
Use /dev/shm for builds, or a /usr/obj.

robert

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