persistence and custom kernel

[jordipujolp at gmail.com (Jordi Pujol)]

El Friday 18 January 2008 02:23:18 Santiago Andres Triana va escriure:
> Hi Jordi (and list)
>
> I will try your instructions.
>
> My most immediate problem though is persistence. And I have some questions:
>
> 1. Is the disk (where the persistence file is written) supposed to have a
> particular label? what if it is a usb stick partition... or a NFS
> filesystem?

Persistence is for the home directory or even the whole filesystem,

The whole filesystem persistence is very slow because all the changes are 
written to disk, don't recommend it.

Home persistence does work, and performs very well, even better than disk 
installed OSs, because only the user documents and settings are written to 
disk, the rest is done in RAM memory.
In an unmodified live system has the label 'home-rw', but we can modify 
the /etc/live.conf file assigning other values. Ex.

home_persistence="santiago-rw"

if it is a USB partition that works the same, with the partition label; only 
is necessary to wait for the operating system mounting the usb devices,
Modify the /etc/live.conf with:

live-media-timeout=15 (not sure if is that variable?)

mounting a persistent nfs partition is not supported directly, should modify 
something for achieve that.

>
> 2. Are the labels different if the live-snapshot script is used?

I prefer do not work with live snapshots because that writes the disk at the 
end of the sesssion; indeed, a home persistence works like a normal directly 
attached filesystem.

>
> 3. Are you supposed to do something in particular to recover the modified
> system after a reboot or is it automatic when using live-snapshot?
>
I believe no, but i don't recommend live snapshots,

>
> I would not need the persistence feature if I had enough knowledge to
> include my own /etc/network/interfaces file and other things. I wish there
> was some documentation about this...

it's easy to include files creating an additional file of ext2 or ext3 type, 
or even a simple directory.

example, create in the live-media-path a directory with any name and the 
extension ".dir"

mkdir -p live/myfiles.dir

mkdir -p live/myfiles.dir/etc/network/
cp /etc/network/interfaces live/myfiles.dir/etc/network/

or create a subdirectory for the hostname and include files for the live 
filesystem for that host,
debian live will search for additional filesystems in the subdirectory 
corresponding to the live hostname

mkdir -p live/myhostname

  cd /tmp
# the directory hostfiles will contain the filesystem structure
  mkdir -p /tmp/hostfiles
  mkdir -p //tmp/hostfiles/etc/network
  cp /etc/network/interfaces  //tmp/hostfiles/etc/network
  export COUNT=$[$(du -s hostfiles | awk '{ print $1 }' )*2+1000]
  echo $COUNT
# the hostfiles.et3 file will be included in the live filesystem
  dd if=/dev/zero of=hostfiles.ext3 count=0 seek=$COUNT
  mkfs.ext3 -F hostfiles.ext3
  mkdir dir
  mount -o loop hostfiles.ext3 dir
  cp -a hostfiles/* dir
  rm -Rf dir/lost+found
  umount dir

cp hostfiles.ext3 live/myhostname

that is an idea, it's your turn to work about that,

>
> Infinite thanks!
>
> Santiago

Regards,

Jordi Pujol