Quick question about root account.

BigBack666 · 04-01-2012, 04:49 PM

Hey I guys I'm just getting started using linux on ubuntu 11.10 and I have a quick question. Lets say I have two accounts named tegan and sara. If I am logged in as tegan with access to the root account would I then be able to login as sara and also have access to the root? I'll try to explain this through the command line but remember I'm new!

tegan@pc:~$ su
passwd:
root@tegan:/home/tegan# login sara
passwd:
sara@tegan:~$ su

Would this be a possible command?

also would an account only be able to execute a "sudo" command if it has not been able to access the root yet?

Thanks guys and I'm looking forward to more questions in my new adventure with linux!

suicidaleggroll · 04-01-2012, 04:54 PM

If you activated the root account, anybody could log in as root (assuming they have the password). So I'm not really sure what you're asking. Root is just another user (albeit with special privileges). You use "su" to switch between users, "su" without an argument switches to the root user (assuming it's been activated, it isn't by default on Ubuntu).

Once the root user has been activated, anybody on the system can type "su" at the command prompt, enter the root password, and become root.

BigBack666 · 04-01-2012, 05:05 PM

I guess what I was asking was say I was logged in as sara under tegan with root and I was trying to do a sudo command under sara but the system responded with "sara is not in the sudoers file." Is this because sara has not accessed root yet?

suicidaleggroll · 04-01-2012, 05:09 PM

Switching users to root is completely different than being in the sudoer file and having sudo privileges.

sudo is a way to run super-user commands with only your regular user password
root is a separate user account that always has super-user privileges, and has its own password

You can log in as root from any user, and log in as any user from root, without affecting anybody's ability or inability to run sudo. sara's inability to run sudo is because sara is not in the sudoer file, it's not because that user has or has not su'd into the root account before.

I hope that makes sense. Part of the confusion might stem from the "su" acronym. In the case of the "su" command, "su" stands for switch user. It's the program used to switch to any other account on the system. You could type "su sara", or "su tegan" to switch to those users, or if left without an argument it defaults to root, same as typing "su root", ie: "switch user to root".

In the case of the "sudo" command, "su" stands for super-user, ie: "super-user do".

BigBack666 · 04-01-2012, 05:15 PM

Alright I think I get it now thanks! I've always thought su only stood for superuser.

jmc1987 · 04-01-2012, 05:56 PM

su does stand for super user which makes you go root. But by default its disabled in Ubuntu. sudo is just a program designed to give a user predifined elevated privages. Which technically sudo doesn't make you root just gives you some root powers. "$sudo -f" will give you a root shell though if allowed via /etc/sudeors file.

suicidaleggroll · 04-01-2012, 06:15 PM

Quote:

Originally Posted by jmc1987

su does stand for super user which makes you go root.

The program "su" does not stand for super user, it stands for switch user or substitute user. Nothing about that program is particular to root or the super user, except that if you call it without providing an argument, it defaults to root.

Code:

$ man su

NAME
       su - run a shell with substitute user and group IDs

SYNOPSIS
       su [OPTION]... [-] [USER [ARG]...]

DESCRIPTION
       Change the effective user id and group id to that of USER.

blah blah blah

       If USER not given, assume root.

chrism01 · 04-01-2012, 06:29 PM

What he said; eg you can switch from user1 to uiser2 without invoking any rootly powers, you just need acctname+passwd.

Incidentally

Code:

su <user>

logs you in as target user, BUT with src user's env.
To get target user's env, insert '-' thus

Code:

su - <user>

frankbell · 04-01-2012, 07:21 PM

Just as an aside, my understanding is that, by default, Ubuntu puts the first user created (normally the user name picked by the person installing the software) in the sudoers file. Additional users must be added to sudoers by the priviledged user with sudo visudo.

TobiSGD · 04-01-2012, 08:18 PM

Quote:

Originally Posted by chrism01

What he said; eg you can switch from user1 to uiser2 without invoking any rootly powers, you just need acctname+passwd.

Incidentally

Code:

su <user>

logs you in as target user, BUT with src user's env.
To get target user's env, insert '-' thus

Code:

su - <user>

Come on, chrism01, you were the one that initiated the "Use proper English"-rule, now you should stick with it.

chrism01 · 04-01-2012, 08:43 PM

Ouch .. actually I haven't checked that thread since my last post there ....
I admit I was thinking more of 'c u' 'ur' etc (assuming 'etc' is an acceptable shortening of et cetera).
Its always difficult to agree what abbreviation are acceptable & which aren't, although (technical) acronyms at least should be allowed.
In any case, it was only a suggestion for discussion, not a 'we must do this', if you see my posts there.

Just checked: LQ rules have not been amended yet ..

jmc1987 · 04-01-2012, 08:49 PM

Quote:

Originally Posted by suicidaleggroll

The program "su" does not stand for super user, it stands for switch user or substitute user. Nothing about that program is particular to root or the super user, except that if you call it without providing an argument, it defaults to root.

Code:

$ man su

NAME
       su - run a shell with substitute user and group IDs

SYNOPSIS
       su [OPTION]... [-] [USER [ARG]...]

DESCRIPTION
       Change the effective user id and group id to that of USER.

blah blah blah

       If USER not given, assume root.

Yes you are correct I totally slipped. I guess I've always referred to it as "Super User" as it use it to access any account including root.