# mount | grep target
/dev/sda1 on /target type ext4 (ro,noatime,errors=remount-ro,barrier=1,data=ordered)
# umount /target
umount: can't umount /target: Device or resource busy
# lsof /target
/bin/sh: lsof: not found
# /target/usr/bin/lsof /target
COMMAND <etc/>
lsof <etc/>
lsof <etc/>
# which umount
/bin/sh: which: not found