Whenever I attempt to su to root by using su while logged in as a regular user on my Debian machine it silently fails, dumping me back into my original user and shell. While searching for this problem I came across solutions that explained that this behaviour is supposed to happen if the user I attempting to login to has an invalid shell in /etc/passwd, which doesn't seem to be the case, the first line on the file is: root:x:0:0:root:/root:/bin/bash.

The only way I can su to root is with:

su -s /bin/sh

Since it looks like the problem is with the bash installation itself, I tried reinstalling bash with apt-get install --reinstall bash while logged in as root, but the error still persists. How can I make it possible to login to root using bash with just su?

I just noticed that if during the timespan between hitting enter after entering root password and being dumped back into my original user I try hitting ctrl+c, su works and I am logged in as root in bash.

If I'm logged in as root using a shell, and run /bin/bash from there, it returns me a Segmentation fault error.

I tried running /bin/bash -x. It seems to run forever printing /opt/spark//bin:/opt/spark//bin:/opt/spark//bin. When forced to stop with ctrl+c, it runs bash with root user as if nothing happened. strace /bin/bash seems to be showing that the command tries to open /root/.bashrc over and over again until it segfaults.

  • Have you checked (with cat -et for example) that there are no trailing non-printing characters (such as a stray carriage return) on the password entry? – steeldriver Mar 9 '18 at 18:20
  • The first two lines of output of cat /etc/passwd -et are root:x:0:0:root:/root:/bin/bash$ daemon:x:1:1:daemon:/usr/sbin:/usr/sbin/nologin$ – Vinícius Aguiar Mar 9 '18 at 18:23
  • Is /bin/bash in /etc/shells? – Andy Dalton Mar 9 '18 at 18:29
  • 2
    That's probably the problem; su runs your shell, which segfaults. – Jeff Schaller Mar 9 '18 at 18:36
  • 1
    You may try /bin/bash -x to see if there's something in the login profiles that is segfaulting; otherwise, strace could help if bash itself is segfaulting. – Jeff Schaller Mar 9 '18 at 18:58

Your problem stems from an infinite loop in your ~/.bashrc file:

export SPARK_HOME=/opt/spark/ 
export PATH=$PATH:$SPARK_HOME/bin 
source ~/.bashrc

When placed in your ~/.bashrc file, you'll successfully su to the user and run your shell, but you'll never get a prompt.

The minimal fix would be to comment out the source line.

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.