I have the same problem (though note that the configure script does in fact exit without an error despite printing the error to the console. I have to use dpkg-reconfigure to reproduce the error. I assume my system isn't bootable but I'm not eager to test this):
root@tweedle:~# dpkg-reconfigure initramfs-tools update-initramfs: deferring update (trigger activated) Processing triggers for initramfs-tools (0.133+deb10u1) ... update-initramfs: Generating /boot/initrd.img-3.16.0-6-amd64 cryptsetup: ERROR: Couldn't resolve device rootfs My /etc/mtab is indeed a symlink to /proc/self/mounts root@tweedle:~# ls -l /etc/mtab lrwxrwxrwx 1 root root 19 Aug 24 2017 /etc/mtab -> ../proc/self/mounts root@tweedle:/home/stark# cat /proc/self/mounts rootfs / rootfs rw 0 0 sysfs /sys sysfs rw,nosuid,nodev,noexec,relatime 0 0 proc /proc proc rw,nosuid,nodev,noexec,relatime 0 0 udev /dev devtmpfs rw,nosuid,relatime,size=1984220k,nr_inodes=496055,mode=755 0 0 devpts /dev/pts devpts rw,nosuid,noexec,relatime,gid=5,mode=620,ptmxmode=000 0 0 tmpfs /run tmpfs rw,nosuid,noexec,relatime,size=399172k,mode=755 0 0 /dev/mapper/tweedle--vg-root / ext4 rw,relatime,discard,errors=remount-ro,data=ordered 0 0 securityfs /sys/kernel/security securityfs rw,nosuid,nodev,noexec,relatime 0 0 tmpfs /dev/shm tmpfs rw,nosuid,nodev 0 0 tmpfs /run/lock tmpfs rw,nosuid,nodev,noexec,relatime,size=5120k 0 0 tmpfs /sys/fs/cgroup tmpfs ro,nosuid,nodev,noexec,mode=755 0 0 cgroup /sys/fs/cgroup/systemd cgroup rw,nosuid,nodev,noexec,relatime,xattr,release_agent=/lib/systemd/systemd-cgroups-agent,name=systemd 0 0 pstore /sys/fs/pstore pstore rw,nosuid,nodev,noexec,relatime 0 0 cgroup /sys/fs/cgroup/cpuset cgroup rw,nosuid,nodev,noexec,relatime,cpuset 0 0 cgroup /sys/fs/cgroup/net_cls,net_prio cgroup rw,nosuid,nodev,noexec,relatime,net_cls,net_prio 0 0 cgroup /sys/fs/cgroup/cpu,cpuacct cgroup rw,nosuid,nodev,noexec,relatime,cpu,cpuacct 0 0 cgroup /sys/fs/cgroup/devices cgroup rw,nosuid,nodev,noexec,relatime,devices 0 0 cgroup /sys/fs/cgroup/perf_event cgroup rw,nosuid,nodev,noexec,relatime,perf_event 0 0 cgroup /sys/fs/cgroup/freezer cgroup rw,nosuid,nodev,noexec,relatime,freezer 0 0 cgroup /sys/fs/cgroup/blkio cgroup rw,nosuid,nodev,noexec,relatime,blkio 0 0 systemd-1 /proc/sys/fs/binfmt_misc autofs rw,relatime,fd=31,pgrp=1,timeout=0,minproto=5,maxproto=5,direct 0 0 debugfs /sys/kernel/debug debugfs rw,relatime 0 0 hugetlbfs /dev/hugepages hugetlbfs rw,relatime 0 0 mqueue /dev/mqueue mqueue rw,relatime 0 0 sunrpc /run/rpc_pipefs rpc_pipefs rw,relatime 0 0 /dev/sda1 /boot ext2 rw,relatime 0 0 tmpfs /run/user/122 tmpfs rw,nosuid,nodev,relatime,size=399168k,mode=700,uid=122,gid=126 0 0 gvfsd-fuse /run/user/122/gvfs fuse.gvfsd-fuse rw,nosuid,nodev,relatime,user_id=122,group_id=126 0 0 fusectl /sys/fs/fuse/connections fusectl rw,relatime 0 0 tmpfs /run/user/1000 tmpfs rw,nosuid,nodev,relatime,size=399168k,mode=700,uid=1000,gid=1000 0 0 gvfsd-fuse /run/user/1000/gvfs fuse.gvfsd-fuse rw,nosuid,nodev,relatime,user_id=1000,group_id=1000 0 0 binfmt_misc /proc/sys/fs/binfmt_misc binfmt_misc rw,relatime 0 0 -- greg