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30 lines
1.5 KiB
Markdown
30 lines
1.5 KiB
Markdown
# Rationale
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By default, the ONL file system is NOT persistent, meaning that if you
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reboot, your changes will dissapear (!!). While this may sound suboptimal
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at first, it does have the incredibly nice property of ensuring that many
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classes of configuration and other problems can go away with a reboot.
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This is particularly nice when you have a switch that may be headless
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(no permanently connected console cable or keyboard).
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ONL accomplishes this with OverlayFS
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(https://www.kernel.org/doc/Documentation/filesystems/overlayfs.txt).
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As described at http://opennetlinux.org/docs/bootprocess, the ONL
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switch image (.SWI file) contains a read-only root file system image.
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The default ONL root file system is then a copy-on-write (using overlayfs)
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view into that file system image.
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It has the following properites:
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* Any file that is editted/removed/etc is transparently copied into a RAM disk via overlayfs
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* Thus, any changes to files appear as you would expect, until a reboot
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* Any file that is uneditted remains backed by the /mnt/onl/data file system, so you
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do not need to have enough RAM to store the entire rootfs. This is important with
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switches that do not have much RAM to begin with.
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If you want to persist files, you can either install the image directly to disk using
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the Installed installer, put debian files to the /mnt/onl/data/install-debs directory.
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Or use rc.boot files to do system management (/mnt/onl/$dir/rc.boot)
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Packages present and listed in /mnt/onl/data/install-debs/list will be installed.
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