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Thread: change boot time ramdisk size howto

  1. #1
    Junior Member
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    change boot time ramdisk size howto

    Hi,
    I have 8G of ram
    at boot Knoppix (7.6) makes a ramdrive of 4G ... but I kinda need 5G

    any solution to change ramdisk size ?

  2. #2
    Senior Member registered user
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    Quote Originally Posted by sorcerer View Post
    at boot Knoppix (7.6) makes a ramdrive of 4G ... but I kinda need 5G
    A 4 Gb limit may be to prevent its being used to contain a single file larger than 4 Gb.
    4 Gb is a filesize limitation of fat32 or vfat filesystems.
    Does this have any bearing on your question?

  3. #3
    Senior Member registered user
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    Hi sorcerer!

    How did you find out the size of the ramdisk?

    When I booted Knoppix 7.6.0 in Virtualbox 5.0.10 with 8 GB of RAM the command
    Code:
    df -h
    showed that the /ramdisk is 6.3 GB large.

  4. #4
    @klaus2008
    What a good catch regarding the ratio of 4GB to 8GB mentioned in sorcerer's post! But, with KNOPPIX 7.4.2, a ram with physical size of 4096MB can only be recognised as 3246MB when running in 32-bit mode and 3631MB in 64-bit mode. If the latest KNOPPIX is able to see all 4GB by default, that's awesome!

    @sorcerer
    From my very limited understanding of Linux and KNOPPIX, the default size of ramdisk is 80% of the ram size recognised by the kernel when the physical ram size is greater than 2000MB. If setting the ramdisk size manually is of interest, you could have a look at the /init file and keep an eye on the keywords of ramdisk and RAMDISK. The syntax of this hidden cheatcode is a bit tricky; the init script can take floating-point number, whereas the mount command only understands integer. One big question which keeps popping up in my head is what if the used space of ramdisk is larger than the ram size recognisable by the kernel but is still within the physical ram size... As I am not 100% sure what I'm talking about, so do it with your own risk... Sorry for the cliché...

  5. #5
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    @utu nope, they don't, this is about 8G ram and ram only, no connection with vfat
    @klaus2008 you have A REALLY GOOD POINT, yes, there is a /ramdisk with 6.3G, but / is exactly half memory (4G if you have 8G, and 8G if you have 16G)

    so, changing the question:
    is it safe to use /ramdisk and / in the same time as they are more with 25% than total memory ? (4+6 = 10, and total memory is 8 )
    is there any solution to modify them at boot time ?


    now this is just curiosity, I bet I can use those 5G in /ramdisk, thank you for actually solving it
    Last edited by Werner P. Schulz; 12-07-2015 at 05:24 PM.

  6. #6
    Junior Member
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    please edit my post and change:
    (4+6 = 10, and total memory is
    to
    (4+6 = 10, and total memory is 8 )

    thank you

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