A question about "sudo" and "su" commands.

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hack3rcon
Posts: 530
Joined: 2015-02-16 09:54

A question about "sudo" and "su" commands.

#1 Post by hack3rcon »

Hello.
Why with "sudo" command some tasks can't be done? For example:

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$ sudo cat /dev/null > sources.list
bash: sources.list: Permission denied
Thank you.

peter_irich
Posts: 1327
Joined: 2009-09-10 20:15
Location: Saint-Petersburg, Russian Federation

Re: A question about "sudo" and "su" commands.

#2 Post by peter_irich »

sudo has no effect to redirection. It is possible to bypass, but I not remember how, I prefer use root with "su -".

Peter.

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Head_on_a_Stick
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Re: A question about "sudo" and "su" commands.

#3 Post by Head_on_a_Stick »

Try

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sudo sh -c 'cat /dev/null > sources.list'
Or with su:

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su -c 'cat /dev/null > sources.list'
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hack3rcon
Posts: 530
Joined: 2015-02-16 09:54

Re: A question about "sudo" and "su" commands.

#4 Post by hack3rcon »

peter_irich wrote:sudo has no effect to redirection. It is possible to bypass, but I not remember how, I prefer use root with "su -".

Peter.
Thanks.

theblueplll
Posts: 154
Joined: 2019-04-29 01:17

Re: A question about "sudo" and "su" commands.

#5 Post by theblueplll »

Or

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sudo su
hit enter then type your password
and any command under the sun that is supported by your OS will work

Just remember

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exit
when you're finished to log out of being root

AND be careful what you do there is no "you shouldn't do this" warning in LInux when using the terminal LoL

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Head_on_a_Stick
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Re: A question about "sudo" and "su" commands.

#6 Post by Head_on_a_Stick »

theblueplll wrote:

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sudo su
That won't work properly for Debian buster because PATH won't include the sbin directories (although it will work for the specific example given in the OP). And using both sudo and su together is just silly.

To attain a root shell with the correct PATH & IFS set then use either

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sudo -i
Or

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su -
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Dai_trying
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Joined: 2016-01-07 12:25

Re: A question about "sudo" and "su" commands.

#7 Post by Dai_trying »

Both sudo su and sudo i give me same results on my Buster Xfce installation. But i'm not arguing in favour of using sudo su, just saying...

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dai@Buster:~$ sudo su
[sudo] password for dai: 
root@Buster:/home/dai# echo $PATH
/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin
root@Buster:/home/dai# exit
exit
dai@Buster:~$ sudo -i
root@Buster:~# echo $PATH
/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin
root@Buster:~# exit
logout
dai@Buster:~$ 

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GarryRicketson
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Re: A question about "sudo" and "su" commands.

#8 Post by GarryRicketson »

And using both sudo and su together is just silly.
Agree, it is pointless, "su" logs you in as root, and "sudo", gives the logged in user root permissions, assuming sudoers ,etc is all set up correctly.
So what is the point of using "sudo", to just use "su", when all one really needed to do is type in "su" in the first place. It just does not make sense at all to me why anyone would think they need to use "sudo", to run the "su" command, where do people get these ideas ?
Just remember

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    exit 
when you're finished to log out of being root
That is the main point and reason for using "sudo", if one uses sudo , they do not need to type "exit", they stop being sudo, after they run the command.
And another thing, while I am at it,
AND be careful what you do there is no "you shouldn't do this" warning in LInux when using the terminal LoL

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man su 
=====

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man sudo
if the admin does not have enough sense and logic, to read the manual and learn the correct options, etc,..they really should not be using either one, and certainly should not be in the sudoers file to start with.
Besides that, the OP could have just used these keywords:

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How to use su and sudo on Debian correctly 
Into their favorite search engine, please at least try to do some searches before asking, there is plenty of good documentation on using su or sudo, all ready written.
The first hit on "sudo" :https://wiki.debian.org/sudo
Another good one: https://www.rootusers.com/the-differenc ... -in-linux/
And there are more, please note, in neither of the above do they say anything about using "sudo su", that is absurd

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Head_on_a_Stick
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Re: A question about "sudo" and "su" commands.

#9 Post by Head_on_a_Stick »

Dai_trying wrote:Both sudo su and sudo i give me same results on my Buster Xfce installation.
Yes, of course, sudo will set PATH & IFS. Thanks for the correction.
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theblueplll
Posts: 154
Joined: 2019-04-29 01:17

Re: A question about "sudo" and "su" commands.

#10 Post by theblueplll »

Head_on_a_Stick wrote:
theblueplll wrote:

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sudo su
That won't work properly for Debian buster because PATH won't include the sbin directories (although it will work for the specific example given in the OP). And using both sudo and su together is just silly.

To attain a root shell with the correct PATH & IFS set then use either

Code: Select all

sudo -i
Or

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su -
I did not know this.
I had been doing it because I saw it somewhere(I think theres something in the link in your sig about not doing that)I think idk.

Anyway the root account is locked on my machine so

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:~$ su
Password: 
su: Authentication failure
I get that when I try to su.

But I see that

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sudo -i
Gives me a root shell like you said so I guess I'll be using that now if that is the proper command.

Thank you for correcting me.

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