How to set the default root password

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By default on buildroot there is no password for root user. It is not really secure and can be a problem for some packages like dropbear. This page explain how to set a default password on our board.

On target

The straitforward way to set the root password is to login on the board then type :

# passwd 
Changing password for root
New password: 
Bad password: too short
Retype password: 
Password for root changed by root

If your password seems to be too simple for the system it will tell it, but the password is changed.

On host

If we have a big production of APF* to flash with the same default password it will be really painfull to change it on each boards. The best way is then to change it under your rootfs.

  • First we need the debian/ubuntu package whois (wich is installed by default). Then generate the crypted password :
$ mkpasswd 
Mot de passe : 

The hash for password 'toto' is generated. Then we have to put it in our shadow file under rootfs. To do that, edit your file buildroot/output/target/etc/shadow, and replace the line:




If you prefer bearded commands you can also type :

sed -i ’s%^root::%root:3DHrA1GdEo2u6:%’ $TARGETDIR/buildroot/output/target/etc/shadow
  • Then regenerate your rootfs.
  • You will then need a password for root when you will run your board.