fuente del sistema ubuntu: solución no encontrada
1. El shell de Ubuntu es Dash Shell por defecto
$ ls -l /bin/sh
lrwxrwxrwx 1 root root 4 1月 22 2019 /bin/sh -> dash
2. Modifique el shell a Bash Shell bajo la autoridad de root.
sudo dpkg-reconfigure dash
[sudo] password for root:
Removing 'diversion of /bin/sh to /bin/sh.distrib by dash'
Adding 'diversion of /bin/sh to /bin/sh.distrib by bash'
Removing 'diversion of /usr/share/man/man1/sh.1.gz to /usr/share/man/man1/sh.distrib.1.gz by dash'
Adding