su identification

spir denis.spir at
Thu Dec 24 15:12:37 GMT 2009

Thank you very much for this very clear explaination.

Basil Fowler dixit:

> You have confused the two commands.
> su means "switch user" Let us assume that you have three users alpha, bravo 
> and root.  Let us assume for the moment that you are logged in as user alpha 
> and alpha's password is ahpla. Let us also assume that the password for bravo 
> is ovarb, and the password for root is master. I know that these passwords are 
> ridiculous, but this is for example.
> I know that you are using a Debian based distro (Ubuntu) because you are 
> invoking the apt-get command. In such distros the first user alpha is set up 
> as a master user account and often the root account is disabled. This is good 
> for single user machines, but is a PITA for multiuser setups.
> When you use su, if it has no arguments, it assumes that you wish to invoke 
> the root account and will demand Root account's password (in this case MASTER) 
> If you follow su with an account name (such as bravo) will will be prompted 
> for  bravo's password (in this case ovarb). When the correct password for the 
> TARGET account is entered, you will then be running as the target account (to 
> leave, type 'exit' or control-d)
> Now, with distros such as Ubuntu, the root account is disabled, so su does not 
> work. A correct password (equivalent to MASTER) does not exist. You have to 
> type in sudo su. You then will have a root shell, and you can run "make 
> aptget".
> sudo is a program that is designed to solve a difficult administrative 
> problem. How do you give an ordinary user power to perform an action (such as 
> managing printers) that normally requires root privileges without giving him 
> /her complete control over the machine?
> Sudo looks up a special file - readable only by root - /etc/sudoers, which 
> lists who can do what under which conditions, and allows or denies the desired 
> action accordingly.
> In the case of Ubuntu, the /etc/sudoers file states that the first user 
> (alpha) is given permission to do anything provided that ALPHA's password is 
> entered, and everyone else (bravo) nothing.
> To modify the /etc/sudoers file a special editor (visudo) is used, because any 
> error in the format of the file will block sudo - this is intentional.
> To activate the root account - not to be done unless you know what you are 
> doing, the /etc/passwd file has to be modified. A root password will have to 
> be created, and the shell command (usually /bin/false) changed to /bin/bash.
> RedHat based distros such as Mandriva have a separate root password at 
> installation, and each user has a separate password. They use kdesu and su. 
> Sudo has to specially downloaded, because it is only needed in exceptional 
> cases. 
> Hope this helps.
> Basil Fowler
> On Thursday 24 Dec 2009 08:35:24 spir wrote:
> > Hello,
> > 
> > I'm aware this question is ~ OT, not really kde related, but have no idea
> >  where else to post it, and surely many people here know the answer. To
> >  install new software (actually, the language Io, for which there seems to
> >  be no package), I had to type:
> > 
> > su -c "sudo make aptget"
> > 
> > This will not work. I'm asked for a password, then get "su: Authentication
> >  failure". Well, this simply cannot be, for I have only one admin password
> >  AFAIK and it works fine for sudo and kdesudo. I tried an old password I
> >  had long time ago (changed to make it more difficult), in case the one for
> >  'su' may have sticked to old times while the one for sudo has changed, but
> >  it is not accepted neither.
> > 
> > I take the opportunity to ask about the use of 'su' in a normal user
> >  session. Also, is there another way to perform the above action?
> > 
> > Denis
> > ________________________________
> > 
> > la vita e estrany
> > 
> >
> > ___________________________________________________
> > This message is from the kde mailing list.
> > Account management:
> > Archives:
> > More info:
> > 
> ___________________________________________________
> This message is from the kde mailing list.
> Account management:
> Archives:
> More info:


la vita e estrany
This message is from the kde mailing list.
Account management:
More info:

More information about the kde mailing list