[Buildroot] Regarding /dev management
Peter Korsgaard
jacmet at uclibc.org
Sat Mar 9 14:09:45 UTC 2013
>>>>> "E" == Ezequiel Garcia <elezegarcia at gmail.com> writes:
E> Hi everyone,
E> Yesterday I spent a couple hours trying to build my first buildroot fs.
E> In particular, I wanted to use devtmpfs
E> (BR2_ROOTFS_DEVICE_CREATION_DYNAMIC_DEVTMPFS)
E> but found that /dev is not mounted by default in skeleton fs scripts,
E> it should be mounted in inittab before some other things.
E> After some hacking in skeleton files, I managed to get the thing working.
E> Did I miss something? Is this the expected behavior?
E> Notice that I'm using the cpio image output and using the rootfs as in
E> initramfs.
E> In this case, CONFIG_DEVTMPFS=y and CONFIG_DEVTMPFS_MOUNT=y
E> kernel options do not matter, because... (quoting Kconfig)
E> ""This will instruct the kernel to automatically mount the
E> devtmpfs filesystem at /dev, directly after the kernel has
E> mounted the root filesystem. The behavior can be overridden
E> with the commandline parameter: devtmpfs.mount=0|1.
E> This option does not affect initramfs based booting, here
E> the devtmpfs filesystem always needs to be mounted manually
E> after the roots is mounted.""
Indeed, for everything besides initramfs CONFIG_DEVTMPFS_MOUNT does the
right thing, and we don't need to do anything in userspace.
E> Perhaps we can add some hack to add:
E> ::sysinit:/bin/mount -t devtmpfs devtmpfs /dev
E> to skeleton when BR2_ROOTFS_DEVICE_CREATION_DYNAMIC_DEVTMPFS=y.
E> However, being new to buildroot, perhaps I'm speaking non-sense and the
E> developer is expected to use its own custom skeleton in this case.
We already take care of this for initramfs, see fs/cpio/init and the
ROOTFS_CPIO_ADD_INIT rule. Doesn't that work for you?
--
Bye, Peter Korsgaard
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