iB::Topic::odd frugal behaviour...

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Topic: odd frugal behaviour..., one has /bin of /KNOPPIX the other /ram

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cbagger01

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Posts: 4264
Joined: Oct. 2003

Posted: Mar. 02 2006,17:43

The problem, as I understand it, is the creation of the ramdisk file system.

I think there is some internal calculation that gives you "X" number of INodes for every "Y" MB of ramdisk space.

This calculation is not ideal for our needs because the symlinks eat up a lot of INodes even though they don't take up much disk space. I think that calculation was a rule-of-thumb for people who store real files inside the disk, and not a situation where there is a whole lotta symlinking goin' on.

I guess the ideal situation would be to figure out how to manipulate this number and then tweak the linuxrc or other boot script so that it creates more INodes per MB of ramdisk.

But first, we need to understand the ramdisk creation process and the commandline switches that are available to us before the next level of understanding, how to do a "fix", is achieved.

roberts

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Posted: Mar. 02 2006,19:29

The number of inodes is controlled via the initial mke2fs command. Either based on number blocks or a pre-calculated fixed number.
If one was building an image for a specific targeted hardware/software configuration then one could adjust these figues to be most accomodating. When I first built appliances, I used several ramdisks each with varying inode formulas but these applicances ran trageted applications so the inode forumla could be fine tuned. DSL is a general pupose micro desktop capable of expanding to quite a large size. Not sure the effort would show results.

_pathos

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Joined: Aug. 2005

Posted: Mar. 03 2006,11:16

Surely just the usual calculation + the constant number of INodes needed for the symbollic links should be acceptable?

So theoretically I could find the right file in /etc , modify it and remaster the image?

Thanks for the feedback btw its exceptional.

cbagger01

Group: Members
Posts: 4264
Joined: Oct. 2003

Posted: Mar. 05 2006,07:01

From the informatin below,

http://www.linuxdevcenter.com/linux/cmd/cmd.csp?path=m/mke2fs

http://www.die.net/doc/linux/man/man8/mke2fs.8.html

it appears that there are two ways to tackle the problem during the initial creation of the /ramdisk filesystem.

1) Use the -i switch to change the bytes-per-inode ratio to something better than 4096 bytes for every inode

2) Use the normal inode ratio for most of the time, EXCEPT when ramdisk size < X (where "X" is the magic number where you don't have enough indodes by default). When ramdisk size < X , then either tweak the ratio downward OR set a fixed number of inodes using the -N switch.

I like #2 better because it does not change the behavior (inode ratio) for all users, just the specific ones that need the extra inodes.

You should be able to remaster the change wherever the /ramdisk filesystem is created, either inside the minirt24.gz (linuxrc), or later on in one of the init scripts.

If it is inside the minirt24.gz initial ramdisk, you can make your change without the need for a full blown compressed iso remastering.