Im trying to configure a minimal kernel, that will work on a virtme / qemu / kvm stack I did make allnoconfig virtme-configkernel --update then I added BTRFS_FS, since thats the host fs. of course it didnt work. then tried DM, needed MD, added both, again didnt help. so I need to stop just guessing. (admittedly, asking is worse ?) heres how it actually goes: 9pnet: Installing 9P2000 support sched_clock: Marking stable (3466602654, 29303733)->(4050551166, -554644779) Btrfs loaded, crc32c=crc32c-generic, zoned=no 9pnet_virtio: no channels available for device /dev/root VFS: Cannot open root device "(null)" or unknown-block(0,0): error -2 Please append a correct "root=" boot option; here are the available partitions: Kernel panic - not syncing: VFS: Unable to mount root fs on unknown-block(0,0) CPU: 0 PID: 1 Comm: swapper Tainted: G W 5.14.0-rc4+ #5 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.14.0-4.fc34 04/01/2014 Call Trace: dump_stack+0x1b/0x1d panic+0x95/0x202 mount_block_root+0x204/0x268 mount_root+0x5d/0x62 Heres a working kernel (if overlarge config) It has btrfs, md, which is why I took those guesses above zswap: loaded using pool lzo/zbud Key type ._fscrypt registered Key type .fscrypt registered Key type fscrypt-provisioning registered Btrfs loaded, crc32c=crc32c-generic, zoned=yes Key type encrypted registered PM: Magic number: 1:872:1009 RAS: Correctable Errors collector initialized. md: Skipping autodetection of RAID arrays. (raid=autodetect will force) qemu-system-x86_64: warning: 9p: degraded performance: a reasonable high msize should be chosen on client/guest side (chosen msize is <= 8192). See https://wiki.qemu.org/Documentation/9psetup#msize for details. VFS: Mounted root (9p filesystem) readonly on device 0:20. devtmpfs: mounted Freeing unused decrypted memory: 2036K Anybody see any clues ?