RamdiskGreaterThan4MBCausesProblems < DULG

%SECTION0{name=RamdiskGT4MBCausesProblems}% Ramdisk Greater than 4 <nop>MB Causes Problems

   Question:: I built a ramdisk image which is bigger than 4 <nop>MB. I run into
    problems when I try to boot Linux with this image, while other
    (smaller) ramdisk images work fine.

   Answer:: The Linux kernel has a default maximum ramdisk size of 4096 kB. To
    boot with a bigger ramdisk image, you must raise this value. There
    are two methods:
      * Dynamical adjustment using boot arguments:<br>
       You can pass a boot argument
       =ramdisk_size<nop>=&lt;size-in-kB&gt;=
       to the Linux kernel to overwrite the configured maximum.
       Note that this argument needs to be before any =root= argument. A
       flexible way to to this is using U-Boot environment
       variables. For instance, to boot with a ramdisk image of 6 <nop>MB
       (6144 kB), you can define:
       <pre>
%UBOOT_PROMPT% setenv rd_size 6144
%UBOOT_PROMPT% setenv bootargs ... ramdisk_size=\${rd_size} ...
%UBOOT_PROMPT% saveenv
       </pre>
       If you later find out that you need an even bigger ramdisk
       image, or that a smaller one is sufficient, all that needs
       changing is the value of the ="rd_size"=
       environment variable.
      * Increasing the Linux kernel default value:<br>
       When configuring your Linux kernel, adjust the value of the
       =CONFIG_BLK_DEV_RAM_SIZE= parameter so that
       it contains a number equal or larger than your ramdisk (in
       kB).  (In the 2.4 kernel series, you'll find this setting under the
       "Block devices" menu choice while, in the 2.6 series, it will be under
       "Device drivers" -> "Block devices".)
14.3.17. Linux Kernel crashes when using a ramdisk image		1. Abstract		14.3.19. Combining a Kernel and a Ramdisk into a Multi-File Image
Prev		Home		Next