topic rootfs size for IMX8mini Yocto Linux in i.MX Processors

rootfs size for IMX8mini Yocto Linux

13614278 — Fri, 10 Apr 2020 00:29:13 GMT

Sorry I have to raise this question here.

[My case] :

IMX8mini,8G emmc, running Yocto Linux, Linux 4.14.98 BSP

[Problem]:

By default, the Yocto Linux build rootfs is about 1.3GB, when I flashed it to EVK, the whole system showed just 1.3GB, that's definitely unreasonable as my emmc is 8GB.

[The Solution I got so far]

After googling with Yocto, I knew that I can either use IMAGE_ROOTFS_EXTRA_SPACE=" xxxxxx" or IMAGE_ROOTFS_SIZE= "xxx" to extend the whole size.

[My Problem]:

But, if I do that, I found my rootfs would also be forcely enlarged to above file size.

e,g, If I set IMAGE_ROOTFS_EXTRA_SPACE=" xxxxxx" as 8GB, then the build out rootfs image size is also 8GB!!!!!!!!!!!!

That's really bad, as so many useless ZERO-padding for the rootfs, the real rootfs is noly 800MB, why are you padding so many useless data to forcely enlarge to a useless 8GB?????!!!!!!!!!!! That caused me took too much useless time to flash the useless 8GB data to EMMC!!!!!!!!

This is a waste of both flash image time and my hard-disk storage!!!!!!!!!

Why Yocto had such bad design???????

Why not use the Android's smart way????? For Android. the whole system.img is only about 800MB, after it flashed to EVK, the whole system(/) still show 8GB emmc instead of 800MB.

Could anyone help me about this frustrating issue? Thanks a lot.

Re: rootfs size for IMX8mini Yocto Linux

Yuri — Fri, 10 Apr 2020 02:43:34 GMT

Hello,

In any case, using Yocto approach for Linux system generation requires

significant host computer resources. Customers can build file system once
and - if needed - to recompile U-boot and or kernel without Yocto environment,
as described in NXP Linux documentation. Also it is possible to build small size
file system and resize part, using such utility as parted.

Regards,

Yuri.

Re: rootfs size for IMX8mini Yocto Linux

13614278 — Fri, 10 Apr 2020 09:32:27 GMT

Hi Yuri,

Thanks for the help. But for

Also it is possible to build small size
file system and resize part, using such utility as parted.

How to do this? It's difficult for me to get the point. Does it mean there is a tools whose name is "parted" to do this? or something else? I can't get any useful info after I google with "Yocto + parted"

Thanks

Re: rootfs size for IMX8mini Yocto Linux

Yuri — Mon, 13 Apr 2020 03:14:29 GMT

13614278@qq.com

Hello,

below is document, describing to build and use the parted.

Parted User’s Manual

Perhaps it would be easier just to use big size images :-(

Regards,

Yuri.

Re: rootfs size for IMX8mini Yocto Linux

NXP_USER_05 — Sat, 13 Dec 2025 15:12:36 GMT

Hi @Yuri ,

We are working with the i.MX8M Plus EVK, which has 32 MB QSPI flash.
Our goal is to boot U-Boot, Linux kernel, device tree, and initramfs (rootfs.img ) entirely from QSPI flash.

We are able to successfully boot:

U-Boot (from flash.bin)

Linux kernel (Image.gz)

Device Tree (imx8mp-evk.dtb)

However, we are facing issues when loading and using the initramfs/rootfs image from QSPI flash. The kernel starts successfully, but the kernel hangs at Waiting for removable media.... see the below log attached.

-----Flash Layout and Image Sizes----------------

QSPI flash size: 32 MB

flash.bin (U-Boot + SPL) ~2.3 MB
Image.gz (Kernel) ~13.5 MB
imx8mp-evk.dtb ~86 KB
rootfs.img ~12.6 MB

----QSPI Offset Layout----------
flash.bin @ 0x00000000
Image.gz @ 0x00240000
imx8mp-evk.dtb @ 0x01000000
rootfs.img @ 0x01080000

------Programming files into QSPI (from SD card)---------
sf probe 0
sf erase 0x0 0x2000000

fatload mmc 1 ${loadaddr} flash.bin
sf write ${loadaddr} 0x0 ${filesize}

fatload mmc 1 ${loadaddr} Image.gz
sf write ${loadaddr} 0x240000 ${filesize}

fatload mmc 1 ${loadaddr} imx8mp-evk.dtb
sf write ${loadaddr} 0x1000000 ${filesize}

fatload mmc 1 ${loadaddr} rootfs.img # initramfs (cpio.gz)
sf write ${loadaddr} 0x1080000 ${filesize}

------After flashing,power-cycle the board--------------

After boot from u-boot,setting the env variables for Linux kernel (Image.gz),Device Tree (imx8mp-evk.dtb),rootfs.img.

sf probe 0
setenv loadaddr 0x40480000 // kernel
setenv fdt_addr 0x43000000 //dtb
setenv initrd_addr 0x43800000 //rootfs
setenv kernel_comp_addr_r 0x50000000
setenv kernel_comp_size 0x04000000

sf read ${loadaddr} 0x240000 0xCD3CE2

sf read ${fdt_addr} 0x1000000 0x14360

sf read ${initrd_addr} 0x1080000 0xC04DB0

setenv bootargs "console=ttymxc1,115200 root=/dev/ram0 rw"

setenv bootcmd 'sf probe 0; sf read ${loadaddr} 0x240000 0xCD3CE2; sf read ${fdt_addr} 0x1000000 0x14360; sf read ${initrd_addr} 0x1080000 0xC04DB0; booti ${loadaddr} ${initrd_addr} ${fdt_addr}'

saveenv

-----------------------Question 1------------------------------------
1.With SD card Wic file working fine with partitions (Boot/Root).
2.We genarated Two yocto images
==> 1.bitbake core-image-minimal-initramfs (generated initramfs.cpio.gz) this cpio.gx converted into rootfs.img by using this cmd mkimage -A arm -O linux -T ramdisk -d <gzipped_rootfs> <Ramdisk_name> (from linux user guide)
==>2.Also generated tiny rootfs from yocto generated using bitbake core-image-tiny. core-image-tiny-imx8mp-evk.tar.zst this tar extracted into EXT4 partition in SD card succussfully loading tiny rootfs .
3.But as said in 2nd point rootfs.img also put into EXT4 root partition in SD card but not loading the rootfs.

-----------------------Question 2------------------------------------
1.Is this the correct approach to boot an initramfs (rootfs.img) directly from QSPI on i.MX8M Plus EVK?

-----------------------Question 3------------------------------------
3.Is there any recommended NXP reference image for booting kernel and initramfs entirely from QSPI on i.MX8MP(Linux kernel (Image.gz),Device Tree (imx8mp-evk.dtb),rootfs.img) ?

4. How to load rootfs.img from QSPI flash on I.MX8MP?