minc working directory

minc gets --tempdir(-t) option with WORKDIR, which has below files and directories.

file/dir	type	description	option
pid	file	PID of container's init process	always
root	dir	Container's rootdir mountpoint	always
storage	dir	overlayfs upper layer directory	always
work	dir	overlayfs working directory	always
settings	file	Setting container parameters	always
run.sh	file	startup script for ermine	--qemu
ipv4	file	Assigned IP address (IPv4)	--net
portmap	file	Assigned port(s)	--port
log	file	Container command output(s)	--background
debug	file	debug output when run in background	--background
criu	dir	container checkpinting image	badger
criu.log	file	criu logging output	badger

--keep option keeps these files after exiting container, but pid file will be removed after exit.