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Old 10-20-2000, 08:56 PM   #1
Sonic63
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Registered: Oct 2000
Posts: 1

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Question


Has any seen a howto on booting from a cdrom and then running the system completly without a hard drive.

Using a large ramdisk ( say 200meg )

????

Thanx
 
Old 10-22-2000, 01:10 PM   #2
jeremy
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Registered: Jun 2000
Distribution: Debian, Red Hat, Slackware, Fedora, Ubuntu
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As long as your BIOS supports it just put the cdrom in the drive and turn on the cpu.
 
Old 05-07-2001, 09:43 AM   #3
drthornt
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Registered: May 2001
Location: Toronto
Distribution: RH 7.2
Posts: 33

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Question large ramdisk

I am tring to get the system to "do" a ramdisk greater than 512 megs.

uname -a:
Linux mofo 2.2.14-5.0smp #1 SMP Tue Mar 7 21:01:40 EST 2000 i686 unknown

notes:
anyone have any Idea how/if this was done?

I try:

/etc/lilo.conf:
image=/boot/vmlinuz-2.2.14-5.0smp
label=linuxram
initrd=/boot/initrd-2.2.14-5.0smp.img
read-only
root=/dev/rd/c0d0p1
ramdisk=500000

/sbin/lilo

<reboot>

/sbin/mke2fs -m0 /dev/ram 500000
mount /dev/ram /var/ramdisk

no problem..

i try:

/etc/lilo.conf:
image=/boot/vmlinuz-2.2.14-5.0smp
label=linuxram
initrd=/boot/initrd-2.2.14-5.0smp.img
read-only
root=/dev/rd/c0d0p1
ramdisk=760000

/sbin/lilo

<reboot>

/sbin/mke2fs -m0 /dev/ram 760000
<no errors>

mount /dev/ram /var/ramdisk
and I get:

"Bad fs-type, or too many mounts.."

from the mount command.

I also get this in dmesg but I don't know exactly where it comes from:

"EXT2-fs: Magic mismatch, very weird !"
"VFS: Can't find an ext2 filesystem on dev ramdisk(1,1)."

note: there is enough ram on the machine:

[root@mta ramdisk]# free
total used free shared buffers cached
Mem: 1036192 58748 977444 32104 18968 17384
-/+ buffers/cache: 22396 1013796
Swap: 1052216 0 1052216
[root@mta ramdisk]#

AHH!!!!

Smells like Mr. Gates:

On Ramdisks...

"The default is 4096 (i.e. 4MB) which should be large enough for most needs."
- from http://www.europe.redhat.com/documen...t-HOWTO-3.php3

Ok so I looked around some more:

greabbed the kernel source , grep -r a pile.. found rd.c:

found:

static unsigned long rd_length[NUM_RAMDISKS]; /* Size of RAM disks in bytes */
static int rd_hardsec[NUM_RAMDISKS]; /* Size of real blocks in bytes */
static int rd_blocksizes[NUM_RAMDISKS]; /* Size of 1024 byte blocks */
static int rd_kbsize[NUM_RAMDISKS]; /* Size in blocks of 1024 bytes */

whipped up a litte program to figure out how big an "unsigned long" and an "int" was on my system ( linux rh 6.2 obviously ) , both were 32 bits.

this tells me that the max size is 4294967296 bytes or 4095 Megs, these vars are not the limiting factor.

I have read up at redhat and linuxhq.com.. I have looked for stuff the Chad Page Has written (Chad wrote the ramdisk driver.)

My on ly conclusion is that the limitation is NOT in the radisk code itself but in some related part.

Help!

Any help would be appreciated.

david
 
  


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