proot errors

[fate-think]

when I execute:
login ubuntu
it says:

proot error: execve("/usr/bin/su"): No such file or directory
proot info: possible causes:
  * the program is a script but its interpreter (eg. /bin/sh) was not found;
  * the program is an ELF but its interpreter (eg. ld-linux.so) was not found;
  * the program is a foreign binary but qemu was not specified;
  * qemu does not work correctly (if specified);
  * the loader was not found or doesn't work.
fatal error: see `proot --help`.
proot error: can't chmod '/data/data/com.termux/files/usr/tmp/proot-12866-VnLk42': No such file or directory