ubuntu 14.04 stuck in login loop. Nothing seems to help

Question

just an hour ago, I installed some package which was supposed to solve the problem with dead keys. After that I restarted my laptop and could not log in because of infinite loop with the login page. I can use the user account but what can I do from it?

I cannot access BIOS, booting from USB does not work. I tried to switch from GUI to the shell Str+Alt+F3 and login in using my superuser credentials but sudo is not recognized in the shell. This is the error message I got:

Command ´Sudo´ is available in /usr/bin/sudo this command cound not be located because /usr/bin is not included in the PATH environment variable. Sudo command not found.

Im begging for help.

Solution

1. Try booting from CD/DVD or network.

2. Instead of sudo, try /usr/bin/sudo or add PATH: export PATH=$PATH:/usr/bin

3. Try booting into recovery mode: https://wiki.ubuntu.com/RecoveryMode

4. There is an option in grub to boot into single user mode (as root), usualy it requires adding single to kernel options and updating grub, but I guess it can also be done in grub command line manually.

Comments

[user3428703]

I already saw the answer, nothing of that helped since I cannot use sudo command in the shell.

[steeldriver]

Have you tried executing sudo with the full path i.e. /usr/bin/sudo somecommand? Have you tried resetting your PATH variable from the Ctrl-Alt-F3 login?

[user3428703]

thank you for the response. I had to admit that I switched to ubuntu from Windows 7 only today...had some working experience with ubuntu in the past but Im not a programmer after all. Im just a chemist. I would be grateful for your guidance here. I will try now full sudo path. Not sure I understand how to reset PATH, though?

[user3428703]

looks like I found the root of the problem. ./profile. PATH="$PATH:/home/alex/mipav" PATH="$PATH:/etc/fsl/5.0/fsl.sh" ". /etc/fsl/5.0/fsl.sh" export DIALOG_SLEEP=4

[user3428703]

How to roll back the changes made to the ./profile? Or can I correct the file from the shell?

[steeldriver]

You can reset the default system-wide PATH in the current session by re-sourcing the /etc/environment file i.e. . /etc/environment or source /etc/environment. After that you should be able to make any necessary edits to your ~/.profile file

[user3428703]

It was a very good lesson for me. I edited ./profile in the shell (path was not specified correctly) and after that Im able to log back in to my account again. Thank you so much for your time!

[przemo]

You are 100% right.