On Fri, May 19, 2017 at 12:34:29PM -0400, Colin Walters wrote: > > One of the things that came up when Darrick and I discussed this on > > the weekly ext4 developer's conference call was our mutual wonderment > > that none of the userspace tools implemented a reboot by created a > > tmpfs chroot, pivoting into the chroot, and then unmounting all of the > > remaining file systems. > > On general purpose systems we have a tmpfs chroot already: the initramfs. Aren't we discarding the initramfs after we've pivoted away from it, to save on memory? Keeping the tmpfs chroot around forever would be a waste of memory, and in some cases, especially if you are using a distribution kernel, the initramfs chroot can be rather large. Creating an tmpfs chroot that was only good enough to manage the shutdown would be pretty easy, though; the number of files you would need would be quite very few in number. > That narrows the problem down to keeping `/boot` consistent at > shutdown time. AIUI, a problem here is that XFS doesn't flush the > journal on `syncfs`, only on unmount? And from what I can tell, > even the `XFS_IOC_FREEZE` ioctl won't do that either. I believe the log *is* checkpointed on an XFS_IOC_FREEZE. - Ted
