Hello all, Thanks for the replies and discussion. So following Bernd's suggestion, I tried making a big file to see how big the file system can grow. Using qemu (arm64, I think it will be the same in real machine, it was always almost the same), I tried 'dd if=/dev/zero of=test bs=1M count=768' and I see a file with size 768MB is generated. So it seems it uses the available ram (I had 1GB ram, and the initial file system size was only 19MB) (BTW, I had to do 'mknod /dev/zero c 1 5 in the init script for this) My real board doesn't have disk connected now and we'll be doing things on ram for now. Thank you. Chan Kim
-----Original Message----- From: Nicholas Mc Guire <der.herr@hofr.at> Sent: Monday, January 2, 2023 4:23 AM To: Bernd Petrovitsch <bernd@petrovitsch.priv.at> Cc: kernelnewbies@kernelnewbies.org Subject: Re: How is the size of init ram disk determined when initramfs is used?
On Sun, Jan 01, 2023 at 06:32:55PM +0100, Bernd Petrovitsch wrote:
Hi all!
On 07/10/2022 04:32, Chan Kim wrote: [...]
I'm using initramfs.cpio.gz for initial file system image. I embed it in the kernel Image file. After linux boots, when I'm in the shell, I can create files. But I'm curious how much the file system can grow.
Why not just try it once;-)
ramdisks are static - so if you mount ram0 and ramdisk_size=8192 then your ramdisk is occupying 8MB and that will be the hard limit at least on some architectures (x86, I think also arm).
I remember somewhere reading that the initramdisk is made and the initramfs archive is extracted in the ramdisk.
On some architectures you can pass the size as kernel parameter ramdisk_size=#kb and that will then set the size of the ramdisk when you mount it (at boot or during normaal operations).
As I did not find what archtiecture you are refering to this might help - grep for ramdisk_size in Documentations and you should have it. E.g. for arm it is marked as obsolete (arm/boot.rst) but still seems to be supported with CONFIG_DEPRECATED_PARAM_STRUCT set. Wonder what it is being replaced by.
thx! hofrat
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