[U-Boot-Users] Is ramdisk a must or not?
Hi,
I cannot figure out some basic questions on ramdisk by reading ramdisk & initrd documents in linux tree and linux-ppc maillist.For the sake of more detailed explanation on ramdisk from DULG and this maillist,I post the topic here for some help.Sorry for bothering you all.
1.Is ramdisk a must or not for embedded application?In URL http://www.redhat.com/docs/manuals/linux/RHL-7.3-Manual/custom-guide/s1-cust...
and some web pages,they say an initrd image is needed for loading your SCSI module at boot time.So if I didn't use SCSI module,I would save the initrd image.Is that so?
2.What advantage does ramdisk have?In which situation should we use it?
3.After programming SELF 8xx image(from ftp.denx.de) to flash on lite_dw,u-boot+kernel+ramdisk worked fine on LCD panel(Thanks wolfgang providing such a workable ramdisk).It displayed "Application running".What does application refer to?Busybox or ramdisk itself?If I want to make my added application in ramdisk run automatically,how should I do?
Any advice is appreciated!
Best regards,
Sam
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On Mon, Feb 02, 2004 at 11:02:28PM +0800, Sam Song wrote:
1.Is ramdisk a must or not for embedded application?
No, you don't need a RAM-disk. U-Boot can directly boot from a flash partition (for example a cramfs or JFFS2 partition).
and some web pages,they say an initrd image is needed for loading your SCSI module at boot time.So if I didn't use SCSI module,I would save the initrd image.Is that so?
In embedded applications you normally _know_ which hardware you have, so either compile it directly into the kernel or load your module from a script while starting.
2.What advantage does ramdisk have?In which situation should we use it?
Initrds were invented for distributors; they normally don't know which hardware the user boots on, but have to supply drivers for every possible device.
Robert
Hello,Robert Schwebel,
You wrote:
No, you don't need a RAM-disk. U-Boot can directly boot from a flash partition (for example a cramfs or JFFS2 partition).
Thank you a lot.That's really what I want to do next.
Initrds were invented for distributors; they normally don't know which hardware the user boots on, but have to supply drivers for every possible device.
So magic. But for the sake of saving flash,I have to remove it from my application.
Best regards,
Sam
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In message 20040202150228.41627.qmail@web15203.mail.bjs.yahoo.com you wrote:
1.Is ramdisk a must or not for embedded application?In
It is definitely NOT a must. There are many ways where to put the root filesystem. The ramdisk may be one of the most simple ways to get started, but there are very few projects whereit is the optimal solution.
In general, using a ramdisk is NOT optimal.
and some web pages,they say an initrd image is needed for loading your SCSI module at boot time.So if I didn't use SCSI module,I would save the initrd image.Is that so?
Please don't compare things that have nothing to do with each other. Booting a general purpose system is one thing (here you have one generic kernel image which will have to work on many, many different hardware configurations, and extensive use of driver modules is a must), while an embedded system is a completely different story (here you have one fix hardware configuration and normally you don't use any modules at all).
2.What advantage does ramdisk have?In which situation should we use it?
It is easy to build and to test.
I cannot think of a situation where a ramdisk image is the best way to go for embedded systems.
ramdisk).It displayed "Application running".What does application refer to?Busybox or ramdisk itself?If I
Application refers to the "/bin/application" script.
want to make my added application in ramdisk run automatically,how should I do?
Add it, and make sure it gets started (like by editing /etc/inittab).
Best regards,
Wolfgang Denk
participants (3)
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Robert Schwebel -
Sam Song -
Wolfgang Denk