shell script how to switch users?

[Rajiv Jaisankar]

Hi All,
i am not sure if this is the right mailing list for asking this question. I
would appreciate any help on this.

I want to switch users using a shell script, i.e.
Say i am logged in as user1. I would like to say su - user2 in my script.
I would be performing some operations as user "user2" as part of the script
after logging in as this user.
Finally i will be exiting back to user1 shell.

How will i login as user2 through shell script?
How will i  execute scripts as user2 after logging in from shell script?
Even if i am able to login as user2
any commands after "su - user2" are not executed as user2. They are executed
only as user1 when i exit the
user2 shell.

-- 
Regards,
Rajiv

[Jacques B.]

On 1/4/07, Rajiv Jaisankar <rajiv.jaisankar(a)gmail.com&gt; wrote:
>  Hi All,
>  i am not sure if this is the right mailing list for asking this question. I
>  would appreciate any help on this.
>
>  I want to switch users using a shell script, i.e.
>  Say i am logged in as user1. I would like to say su - user2 in my script.
>   I would be performing some operations as user "user2" as part of the script
>  after logging in as this user.
>  Finally i will be exiting back to user1 shell.
>
>  How will i login as user2 through shell script?
>  How will i  execute scripts as user2 after logging in from shell script?
>  Even if i am able to login as user2
>  any commands after "su - user2" are not executed as user2. They are executed
>  only as user1 when i exit the
>  user2 shell.
>
>  --
>  Regards,
>  Rajiv
>  --
>  fedora-list mailing list
>  fedora-list(a)redhat.com
>  To unsubscribe:
>  https://www.redhat.com/mailman/listinfo/fedora-list
>
>  
Use the -c option with su, and call a new script to run as that user.

I tried the following:

test.sh script:
#!/bin/bash
echo "before su"
su root -c ./rootscript.sh
echo "after su"
whoami

rootscript.sh (located in the same directory hence why called by ./rootscript)
#!/bin/bash
echo "now in sub shell"
whoami
echo "exiting sub shell"

It behaved exactly as you'd like.  Within the second script, I was
root running the commands.

Jacques B.

[Jacques B.]

>  Use the -c option with su, and call a new script to run as that user.
In case you aren't sure about that option, use it as follows:

su user2 -c user2script.sh

If you only want to run one command as user2, you could simply insert
that command after the -c instead.

su user2 -c whoami

A side note, if the command is more than one word, you must enclose it
in quotes. For example:

su -c 'find / -name \*.c -print' user2
(obviously the order of -c command and the user is interchangeable).

Jacques B.

[Rajiv Jaisankar]

On 1/4/07, Jacques B. <jjrboucher(a)gmail.com&gt; wrote:
>  On 1/4/07, Rajiv Jaisankar <rajiv.jaisankar(a)gmail.com&gt; wrote:
>  > Hi All,
>  > i am not sure if this is the right mailing list for asking this question. I
>  > would appreciate any help on this.
>  >
>  > I want to switch users using a shell script, i.e.
>  > Say i am logged in as user1. I would like to say su - user2 in my script.
>  >  I would be performing some operations as user "user2" as part of the
> script
>  > after logging in as this user.
>  > Finally i will be exiting back to user1 shell.
>  >
>  > How will i login as user2 through shell script?
>  > How will i  execute scripts as user2 after logging in from shell script?
>  > Even if i am able to login as user2
>  > any commands after "su - user2" are not executed as user2. They are
> executed
>  > only as user1 when i exit the
>  > user2 shell.
>  >
>  > --
>  > Regards,
>  > Rajiv
>  > --
>  > fedora-list mailing list
>  > fedora-list(a)redhat.com
>  > To unsubscribe:
>  > https://www.redhat.com/mailman/listinfo/fedora-list
>  >
>  >
>  Use the -c option with su, and call a new script to run as that user.
>
>  I tried the following:
>
>  test.sh script:
>  #!/bin/bash
>  echo "before su"
>  su root -c ./rootscript.sh
>  echo "after su"
>  whoami
>
>  rootscript.sh (located in the same directory hence why called by ./rootscript)
>  #!/bin/bash
>  echo "now in sub shell"
>  whoami
>  echo "exiting sub shell"
>
>  It behaved exactly as you'd like.  Within the second script, I was
>  root running the commands.
>
>  Jacques B.
>
>  --
>  fedora-list mailing list
>  fedora-list(a)redhat.com
>  To unsubscribe: https://www.redhat.com/mailman/listinfo/fedora-list
>  
Hi,
Thanks a lot for your quick responses.  After executing su - user2 -c
script . I am asked for password for user2. Is there any way through
we can we specify password too with this command.
- Rajiv

[Mike]

On Thu, 4 Jan 2007, Rajiv Jaisankar wrote:

>  Hi,
>  Thanks a lot for your quick responses.  After executing su - user2 -c
>  script . I am asked for password for user2. Is there any way through
>  we can we specify password too with this command.
>  - Rajiv
>  
man sudo

[Jacques B.]

>  Hi,
>  Thanks a lot for your quick responses.  After executing su - user2 -c
>  script . I am asked for password for user2. Is there any way through
>  we can we specify password too with this command.
>  - Rajiv
>
>  --
>  fedora-list mailing list
>  fedora-list(a)redhat.com
>  To unsubscribe: https://www.redhat.com/mailman/listinfo/fedora-list
>  
As Mike suggests, you can use sudo.  Then with the option -S to
specify that the password will come from standard input instead of tty
(and then feed it using the < redirect), and the -u user2 to specify
to sudo to user2 instead of to root.  The security vulnerability being
that your password will have to come from somewhere (either within the
script or redirected from within a text file containing the password)
readable. Meaning someone who disects the script can figure out where
to go find the password (if it's not in the script).

There may be a way to do this a bit more securely, but I am not
certain.  I gather the script will run unattended, or will be run by
someone who should not know the password for user2?  If user1 is any
bit curious, he/she will be able to find out the password for user2
quite easily  by examing the script.  Unfortunately the script won't
run without r permission in addition to x permission (I tried with x
but no r and the script will not run).

Jacques B.

[Charles Curley]

On Thu, Jan 04, 2007 at 06:58:53PM +0530, Rajiv Jaisankar wrote:
>  
>     Hi All,
>     i am not sure if this is the right mailing list for asking this question. I
>     would appreciate any help on this.
>     I want to switch users using a shell script, i.e.
>     Say i am logged in as user1. I would like to say su - user2 in my script.
>     I would be performing some operations as user "user2" as part of the script
>     after logging in as this user.
>     Finally i will be exiting back to user1 shell.
>     How will i login as user2 through shell script?
>     How will i  execute scripts as user2 after logging in from shell script?
>     Even if i am able to login as user2
>     any commands after "su - user2" are not executed as user2. They are
> executed
>     only as user1 when i exit the
>     user2 shell. 
First off, please turn off HTML email. Thank you.

To answer your question, create a second script for user2 to
executed. User1 can call it with something like:

su - user2 -c "/full/path/to/user2/script"

run "info su" for more information.

-- 

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