1

He did this last time when I left my laptop at room. Opened the system recovery mode from advanced Ubuntu options and changed the password using 'passwd usrname ' command.Is there anything I can do for this to not happen in future.

Improve this question
7
  • 1
    you can kill him. joking, possible duplicated of askubuntu.com/questions/303654/…
    – Geo
    Aug 15, 2014 at 17:17
  • Heh. This is actually a cool trick. It works for Macs too. I have heard about setting root password, but that causes all sorts of problems in a system. ||| @Geo : Not a dupe at all. That is in regards to not allowing password-setting in Multiuser mode (booted). Root can override that restriction, so it wouldn't help here, nor is it a dupe.
    – Kaz Wolfe
    Aug 15, 2014 at 17:21
  • @Mew what problems does it cause?
    – muru
    Aug 15, 2014 at 17:22
  • @muru Makes it easier to brute-force your system, adds challenges for you, makes hackers think what you're hiding, and causes a few SSH vulnerabilities. (Had a server). Sudo is much safer/easier, but it does allow this feature.
    – Kaz Wolfe
    Aug 15, 2014 at 17:25
  • @Mew What need to brute force if there is no password? SSH by default disallows password authentication for root. Adds only one challenge for the user: remember two passwords.
    – muru
    Aug 15, 2014 at 17:27

2 Answers 2

Reset to default
0

For this user case probably the best "solution" is to re-install Ubuntu with full encryption (LUKS). This would secure the data and prevent changing the root/users password(s).

This could be defeated with a few methods, both hardware (key loggers) and software (custom kernels), but both of those options are unlikely. The OP can assess these risks.

With the above suggestion, I agree with the advice that the ultimate solution is to prevent physical access. In general physical access is root access via any number of techniques.

Improve this answer
1
  • 1
    This is too much effort to deter pranks.
    – muru
    Aug 15, 2014 at 17:50
-1

Yes. Set the root password. Open a terminal, and do:

sudo passwd

Enter a password. Then the root shell in recovery mode will always ask for this password.

Note that all this is futile as he can boot into a live USB and change your password.

Ultimately, given physical access, the security battle is lost.

Improve this answer
6
  • 1
    Block LiveCDs? goes into BIOS | Block BIOS? opens computer and gets HDD | Locked-In HDD? unlocks using lockpicking kit and screwdriver | Encrpyed HDD? cat \dev\null > \dev\sdb. Always a way to do SOMETHING with physical access. My HS tech guy and I would have wars over who could do the worst damage with only physical access.
    – Kaz Wolfe
    Aug 15, 2014 at 17:26
  • Also, you're forgetting about Hirens Boot CD. It has a tool to bypass passwords now.
    – Kaz Wolfe
    Aug 15, 2014 at 17:30
  • @Mew Doesn't prevent anyone from quickly removing the hard disk, attaching elsewhere and doing whatever they want. And adds yet another password for the user to remember. Let me repeat: physical access, the battle is lost. However, for low-grade fun like this roommate, setting a root password is enough, and simplest.
    – muru
    Aug 15, 2014 at 17:30
  • I agree, setting a root password as muru advised is worthless and adds no significant additional security.
    – Panther
    Aug 15, 2014 at 17:42
  • @bodhi.zazen I disagree, since this is enough to deter the casual prank. Anything more is a sledgehammer to kill an ant. While security is important, the context in which this security is setup is also important. Average users don't care. Otherwise we'd all be using full-disk encryption and BIOS passwords and unique passwords for everything, and encrypt all communication.
    – muru
    Aug 15, 2014 at 17:46

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .