Diskless Support for SystemImager

SystemImager does not support natively diskless systems. Ferrol Aderholt has been working on the extension of SIS for such a support. The current implementation only provides some basic diskless configurations; the goal was to have a non-intrusive solution, that you could test easily.

Diskless SystemImager - HowTo

Creation of the configuration file for diskless

The user needs only modify a configuration file. This file is /etc/systemimager/diskless.conf.

< ip > < path_to_kernel > < method_of_boot >

The < method_of_boot > section can define three methods: nfs-root, ramfs-rsync, ramfs-http.

/usr/sbin/si_prepareclient was modified in order to include a flag that can be used to signify whether or not modifications should be done. The proper call is:

/usr/sbin/si_prepareclient --diskless

It looks to see if that flag is there and then calls a function named diskless(). This function makes use of a perl module, /usr/lib/systemimager/perl/SystemImager/Diskless.pm, that contains most of the code that was used in si_mkdiskless. After the function, diskless(), returns si_prepareclient exits. This can be changed, it was just seen as a possible annoyance to have some parts of si_prepareclient to run if the user only wanted the diskless portion to run.

How does it work?

Few details about how each option works:

• NFSRoot:
  • in tftpboot, different directories are: (i) "shared" for the shared file system between nodes and a private directory for each compute nodes (rw). Shared directories are: media mnt scratch selinux srv usr; unshared directories: bin dev etc home lib opt proc root sbin sys var
  • we are using NFsroot, NFSroot is the only solution used _by default_

• ramfs-rsync and ramfs-http: you boot up a minimal image via PXE, then using rsync or http you download the rest the file system. When the file system is in memory (using tmpfs), we switch root to the new file system.

Disclaimer

The current prototype has been fully tested only on Fedora systems. You may encounter issues with other Linux distributions. If such a case, please feel free to contact directly the SRT team.