[Buildroot] Raspberry: sd card image
Arnout Vandecappelle
arnout at mind.be
Tue Jun 28 23:49:17 UTC 2016
On 28-06-16 13:02, David wrote:
> I'm trying to change sdcard image generated by Buildroot for Raspberry and I
> have few questions.
>
> 1) How can I modify size of root filesystem partition? Size option of genimage
> is not working. I always get partition with 5% free space. For example I add size:
>
> partition rootfs {
> partition-type = 0x83
> image = "rootfs.ext4"
> size = 512M
> }
>
> It does not change anything. The partition size is the same as previously.
Are you sure? I think the partition size will be 512M. The filesystem size,
however, will stay the same as before.
To change the filesystem size, use BR2_TARGET_ROOTFS_EXT2_BLOCKS or
BR2_TARGET_ROOTFS_EXT2_EXTRA_BLOCKS.
> 2) I want to add third partition and mount it during boot in read-write mode to
> home directory. Root filesystem is in my case mounted as read-only. I tried add
> to genimage config file:
>
> partition data {
> partition-type = 0x83
> size = 128M
> }
This will create the partition, but won't put a filesystem on it. To add a
filesystem, you have to add an image for it:
image data.ext4 {
ext4 {
# Put any files you want to add here
}
size = 128M
}
...
partition data {
image = "data.ext4"
}
>
> without success. Of course I can do it with other tools (fdisk, mkfs), but I see
> that genimage is now a standard tool in Buildroot to create images.
>
> 3) I think that good idea is mount root filesystem with noatime option.
Actually, that's really a good idea!
> Unfortunately rootflags=noatime does not work.
Doesn't it? That's weird.
> How can I config this option in
> Buildroot? I know that I can modify /etc/fstab using the overlay, but I think
> that there is better way to do it. Do I have to modify /etc/inittab? I noticed
> that Buildroot change this file according to BR2_TARGET_GENERIC_REMOUNT_ROOTFS_RW.
If rootflags doesn't work, then modifying fstab and/or inittab will be the only
option. I'm not sure if 'mount -a' will remount /, so fstab may not be sufficient.
>
> 4) In my system only third partition is mounted in read-write mode, so I want to
> run fsck on this partition before mount to be sure that file system is not
> corrupted by power fail. Should I modify /etc/inittab for this purpose?
Yep.
>
> 5) BTW. I noticed that command tune2fs is not available when
> BR2_PACKAGE_E2FSPROGS_TUNE2FS is selected.
It is in my build. But you probably want the host tune2fs, which is built when
you select BR2_PACKAGE_HOST_E2FSPROGS.
Regards,
Arnout
--
Arnout Vandecappelle arnout at mind be
Senior Embedded Software Architect +32-16-286500
Essensium/Mind http://www.mind.be
G.Geenslaan 9, 3001 Leuven, Belgium BE 872 984 063 RPR Leuven
LinkedIn profile: http://www.linkedin.com/in/arnoutvandecappelle
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