On 03/06/2018 02:34 PM, Theodore Y. Ts'o wrote: > On Mon, Mar 05, 2018 at 08:17:10PM -0800, Randy Dunlap wrote: >> >> ext4_fill_super() tells me: >> >> [ 3.033174] EXT4-fs (sda5): couldn't mount as ext3 due to feature incompatibilities >> [ 3.100186] EXT4-fs (sda5): mounted filesystem with ordered data mode. Opts: (null) >> [ 3.102683] VFS: Mounted root (ext4 filesystem) readonly on device 8:5. >> >> This is a new install, new filesystem. It has never been ext2 or ext3. >> >> After bootup and before I do anything else, I can remount /dev/sda5 on / as >> rw and everything is OK. > > What is the boot command-line that are you using? What does > /proc/cmdline say? Mine says (for example): > > % cat /proc/cmdline > BOOT_IMAGE=/vmlinuz-4.15.3-00026-g373ea7d39542 root=/dev/mapper/cwcc-root ro fbcon=font:sun12x22 quiet Mine says: BOOT_IMAGE=/boot/bzImage-416-3m32 root=/dev/sda5 resume=/dev/sda3 splash=native quiet showopts elevator=cfq selinux=0 apparmor=0 debug initcall_debug ignore_loglevel > The ro mount option is usually what causes the root file system to be > mounted read-only. > > I would check and see whether you are using the same init script path > for your custom kernel versus your distro kernel. In particular, is > the initramfs the same for both? With Debian, there is an initial > ramdisk which is used: > > linux /vmlinuz-4.15.3-00026-g373ea7d39542 root=/dev/mapper/cwcc-root ro fbcon=font:sun12x22 quiet > echo 'Loading initial ramdisk ...' > initrd /initrd.img-4.15.3-00026-g373ea7d39542 My custom kernel does not use an initramfs at all. > With the Debian initial ram disk, e2fsck is actually run on the file > system *before* it is mounted, and then it is mounted under userspace > control, and the kernel's default autoprobing isn't used at all. So > with Debian's initramfs, it *knows* it is an ext4 file system and it > mounts it directly as ext4, so in my kernel logs I just see this: > > Mar 5 18:26:11 cwcc kernel: [ 15.073579] EXT4-fs (dm-1): mounted filesystem with ordered data mode. Opts: (null) > > So I don't see the "VFS: mounting root..." message at all. I don't > know what your distribution is doing, but you might want to check and > see if the "VFS: mounting root" is showing up when you are booting the > distro-kernel. This really smells like a problem with how the > initramfs for your custom kernel was set up... OK, I don't see the "VFS: mounting root" message with the distro kernel. With the distro kernel, I see: [ 10.678700] EXT4-fs (sda5): re-mounted. Opts: data=ordered,acl,user_xattr and with my custom kernel (no initramfs) I see: [ 3.146701] EXT4-fs (sda5): mounted filesystem with ordered data mode. Opts: (null) [ 3.149212] VFS: Mounted root (ext4 filesystem) readonly on device 8:5. so maybe when I'm not using an initramfs, the fs type probing is confused. I'll keep looking into it. Thanks for your time(s). I'll just continue to remount it R/W for now. -- ~Randy
