See LXD issue here for more context: https://github.com/lxc/lxd/issues/3638
After attaching a block device (in my case /dev/sdc3) to a LXD container, the dev-sdc3.device unit is not generated. However, the dev-sdc3.mount unit is generated correctly.
Steps to reproduce (from GitHub issue):
stgraber@castiana:~$ truncate -s 10G test.img
stgraber@castiana:~$ sudo losetup -f test.img
stgraber@castiana:~$ sudo losetup -a
/dev/loop1: [0022]:169383 (/var/lib/snapd/snaps/core_2381.snap)
/dev/loop2: [0022]:770242 (/var/lib/snapd/snaps/core_2312.snap)
/dev/loop0: [0022]:1170310 (/var/lib/snapd/snaps/core_2462.snap)
/dev/loop3: [0045]:309158 (/home/stgraber/test.img)
stgraber@castiana:~$ lxc launch ubuntu:16.04 issue3638
Creating issue3638
Starting issue3638
stgraber@castiana:~$ lxc config device add issue3638 sda unix-block source=/dev/loop3 path=/dev/sda
Device sda added to issue3638
stgraber@castiana:~$ lxc exec issue3638 -- mkfs.ext4 /dev/sda
mke2fs 1.42.13 (17-May-2015)
Discarding device blocks: done
Creating filesystem with 2621440 4k blocks and 655360 inodes
Filesystem UUID: 77832ca2-b16d-4b94-8f7d-9ea08c5e6913
Superblock backups stored on blocks:
32768, 98304, 163840, 229376, 294912, 819200, 884736, 1605632
Allocating group tables: done
Writing inode tables: done
Creating journal (32768 blocks): done
Writing superblocks and filesystem accounting information: done
stgraber@castiana:~$ echo Y | sudo tee /sys/module/ext4/parameters/userns_mounts
Y
stgraber@castiana:~$ lxc exec issue3638 -- mount /dev/sda /mnt
stgraber@castiana:~$ lxc exec issue3638 bash
root@issue3638:~# echo "/dev/sda /mnt ext4 defaults 0 0" >> /etc/fstab
root@issue3638:~# cat /etc/fstab
LABEL=cloudimg-rootfs / ext4 defaults 0 0
/dev/sda /mnt ext4 defaults 0 0
root@issue3638:~# exit
stgraber@castiana:~$ lxc exec issue3638 -- umount /mnt
stgraber@castiana:~$ lxc exec issue3638 -- mount /mnt
stgraber@castiana:~$ lxc stop issue3638
stgraber@castiana:~$ lxc start issue3638
stgraber@castiana:~$ lxc exec issue3638 -- mount | grep mnt
stgraber@castiana:~$ lxc exec issue3638 -- systemctl -a | grep mnt
mnt.mount loaded inactive dead start /mnt
stgraber@castiana:~$ lxc exec issue3638 -- systemctl -a | grep sda
dev-sda.device loaded inactive dead start dev-sda.device
dev-sda.mount loaded active mounted /dev/sda
stgraber@castiana:~$ lxc exec issue3638 -- ps aux | grep udev
root 54 0.0 0.0 41720 1864 ? Ss 16:55 0:00 /lib/systemd/systemd-udevd
stgraber@castiana:~$
Status changed to 'Confirmed' because the bug affects multiple users.