Change password on SD card

[KjeldFlarup]

I have a script to create a RPi SD card from my Intel Linux.
After doing DD, I mound the SD card, and modifies some files.

I would like to change the default password from "raspberry" to something else.

However when I try to modify the passwd file I get an error

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# echo -e "linuxpassword\nlinuxpassword" | passwd -R /media/kfa/rootfs pi
passwd: Cannot determine your user name.

What other tricks exists to change this password?


Kjeld

[GlowInTheDark]

The most straightforward way is to figure out what the second field of the /etc/shadow file should be (by manually changing the password to what you want it to be, then checking the file) and then you can have your script do some sort of automated edit of the mounted /etc/shadow, setting the second field to what you want it to be.

Details left as an exercise for the reader.

[markkuk]

Use the chpasswd command:

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# chpasswd pi:linuxpassword -R /media/kfa/rootfs

[Heater]

As you are doing this from a script how about generating the password hash manually first. For example:

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$ openssl passwd -6 -salt xyz  verysecretpassword
$6$xyz$uOfY4/o3BE1BZ2/cNLbARGNORxJauX6Y7D679TDiUpfcgeDpBAHzAwq4ZQaMlb5TgXzH7G/bU9.sKKftzR9aI0

Then have your script replace the line in /etc/shadow with one that contains that hash string.

Hint, use 'sed' to do that replacement in your script.

The advantage of this is that you won't have a password in plain text embedded in your script for anyone to read. Which is a security hazard. Do remember that password like any other.

See this page for other methods of generating a password hash:
https://unix.stackexchange.com/question ... etc-shadow

[GlowInTheDark]

Then have your script replace the line in /etc/shadow with one that contains that hash string.

Exactly as I said.

Note, BTW, that methods that use a program (e.g., passwd or chpasswd) will need to do some sort of "chroot"ing so they (the program) works on the passwd/shadow files on the mounted drive (SD card) rather than on the system on which you are actually running (which, in OP's case is an x86 Linux box). Although this can, of course, be done correctly and safely by a knowledgeable user, it seems dangerous to recommend to a newcomer. For this reason, it is actually safer to directly edit the file (/path/to/mounted/etc/shadow).