Resources for creating an installable live CD?

Discussion in 'all things UNIX' started by Gullible Jones, Apr 11, 2014.

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  1. Gullible Jones

    Gullible Jones Registered Member

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    I'm looking to create a spin of one of the major distros - probably Debian Testing or Ubuntu LTS, possibly Fedora. I have some ideas for a faster, simpler, and friendlier Linux desktop, and want to test them (and eventually implement them in a working Linux spin).

    What I need is some way of:
    - Creating a live medium
    - Including custom scripts, and changes to the user profile defaults
    - Making it installable (full install to a partition, not just copying the compressed image)

    Or more simply: "I want to turn this customized chroot into a live CD."

    What software is currently available for this, since Remastersys got canned? If the available software turns out not to be up to the job, are there any guides to doing it manually?
     
  2. Gullible Jones

    Gullible Jones Registered Member

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    Last edited: Apr 11, 2014
  3. mirimir

    mirimir Registered Member

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  4. Gullible Jones

    Gullible Jones Registered Member

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    The second procedure borked because of dependency problems with Ubuntu packages. Isn't that stuff supposed to be fixed in LTS? :(

    Anyway I'll try writing a script for the bootcd thing today.
     
  5. Gullible Jones

    Gullible Jones Registered Member

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    THANK YOU @mirimir, it worked! Now I can haz Linux spin.
     
  6. mirimir

    mirimir Registered Member

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    Very cool :)

    Isn't bootcd an amazing thing?

    There's just one tweak that I would love to know how to do. By default, all LiveCDs/DVDs create two ramdisks at boot, each using half of the physical RAM. One ramdisk is used for the unpacked stuff from the LiveCD/DVD. The other one is used for virtual RAM and various temporary folders. With a large LiveDVD, however, at least 8 GB physical RAM is necessary, in order for the first ramdisk to be large enough. Indeed, given that a DVD can hold about 8 GB after compression, having 16 GB physical RAM would be cool. However, in that case, most of the other ramdisk would be totally wasted.

    So, is there some way to change the default, so that the first ramdisk (for stuff from the LiveCD/DVD) is larger than the other ramdisk?
     
  7. Gullible Jones

    Gullible Jones Registered Member

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    Hmm, I don't think there's any way to do that. Too bad.
     
  8. mirimir

    mirimir Registered Member

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    Really?

    How deep is it buried?

    At worst, isn't there some package that could be tweaked and recompiled?
     
  9. lotuseclat79

    lotuseclat79 Registered Member

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  10. mirimir

    mirimir Registered Member

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    By the time that the LiveCD has booted, it's too late to change the ramdisk configuration.

    This choice -- half of RAM for LiveCD contents, and half for temporary stuff -- seems to be hard coded. It's been a while since I looked at the details, but there's nothing that's obviously configurable in the bootcd package.
     
  11. lotuseclat79

    lotuseclat79 Registered Member

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    Hi mirimir,

    The bootcd package appears to be subdivided into the bootcd-mkinitramfs (initramfs extension for bootcd) which is further divided into the initramfs-tools package (tools for generating an initramfs). Perhaps downloading those package sources from the Linux distribution repositories you are using would reveal what you are looking to discover?

    That might be the best and shortest way to get what you want. There is perhaps another long and involved way which would require unwinding the ISO file into its components and looking for the hard coded instantiations (configuration) of the initramfs code.

    I have done the ISO unwinding and created a pae version of an ISO prior to their being generally available from the distribution vendors. Hopefully, you won't need to do both the source code review and the ISO unwinding to confirm your suspicions regarding the hard coding of the parameters in the initramfs code.

    OTOH, there are mailing lists for the various file systems in Linux (Ted T'so being the prime mover for ext3, ext4 filesystem code). Perhaps you could join one of those mailing lists and ask a general question if anyone knows about the initramfs configuration and why it appears to be hard coded into half of RAM for LiveCD contents and half for temporary stuff, and in particular how to modify those parameters in order to reconstruct a special version of bootcd for experimental purposes.

    -- Tom
     
  12. mirimir

    mirimir Registered Member

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  13. lotuseclat79

    lotuseclat79 Registered Member

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    Hi mirimir,

    I used startpage.comto search for "initramfs documentation" which might be of help (links) in your quest.

    -- Tom
     
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