[bash scripting] logging to the virtual account

adash · 05-21-2011, 05:53 AM

Hi guys!
I need to write a bash script that will allow me to manage my "virtual network" (in reality just a bunch of directories and files).

I need to obtain something like : I have my own command 'connect'. We can use it in two different modes: user and admin.

If I type 'connect adashiu virtual_machine_name, computer will ask about password, if password is correct he will change a prompt to :

adashiu_at_virtual_machine_name >

after that user can start to use commands reserved only for user mode.

Analogically with admin mode: prompt 'admin >' and administrator can only use bunch of commands reserved for him.

Can anyone tell me how to solve this problem with changing prompt and separated commands for user and admin ?

Thank you in advance and
sorry for my english

Adam

crts · 05-21-2011, 06:21 AM

Quote:

Originally Posted by adash

Hi guys!
I need to write a bash script that will allow me to manage my "virtual network" (in reality just a bunch of directories and files).

I need to obtain something like : I have my own command 'connect'. We can use it in two different modes: user and admin.

If I type 'connect adashiu virtual_machine_name, computer will ask about password, if password is correct he will change a prompt to :

adashiu_at_virtual_machine_name >

after that user can start to use commands reserved only for user mode.

Analogically with admin mode: prompt 'admin >' and administrator can only use bunch of commands reserved for him.

Can anyone tell me how to solve this problem with changing prompt and separated commands for user and admin ?

Thank you in advance and
sorry for my english

Adam

Hi and welcome to LQ,

what have you tried so far? Where are you stuck?
Not sure what you are exactly trying to do but have you considered using sudo? sudo can not only be used to gain root privileges but also to restrict normal user access. You have to modify the file /etc/sudoers accordingly to allow/restrict users to execute commands.
Type in a terminal

Code:

man sudo
man sudoers

to get more detailed information. You might not have to write a complex script.

adash · 05-21-2011, 07:59 AM

I think that sudo is a command to switch for superuser.

My task to do is :
in file users.txt I have 2 users defined(virtual).

adash|pass|admin
user1|pass|user

i type 'connect user1 machine_name'
then password

If all is ok,
the prompt is changing to 'user1@machine_name >' and the user1 is able only to use custom commands reserved for user.

Hard to explain, hopes you understand me.

crts · 05-21-2011, 08:12 AM

Quote:

Originally Posted by adash

I think that sudo is a command to switch for superuser.

No, it is not. As I wrote in my previous post it can be used to switch to any user.

Anyway, this does sound like homework. Posting homework assignments is against LQ rules.

Since you state that there are no "real" machines (not even virtual machines) involved but just a bunch of directories, my guess is that your instructor has a solution with 'chroot' in mind. Have a look at the manpage:
man chroot

Again, you will have to put in some effort for yourself.
Here is some more reading that will be very helpful:
http://tldp.org/LDP/abs/html/

carltm · 05-21-2011, 08:15 AM

Quote:

Originally Posted by adash

Can anyone tell me how to solve this problem with changing prompt and separated commands for user and admin ?

I don't understand what you want to change.

Do you want the user to not get asked for a password?

Once a user has entered the password, does everything work correctly?
If not, what is not right?

carltm · 05-21-2011, 08:19 AM

Quote:

Originally Posted by crts

No, it is not. As I wrote in my previous post it can be used to switch to any user.

Well, technically sudo isn't the command to switch to any user.
That command is su. Sudo lets you run a single command with
the permissions of root. Of course you can use a combination
of sudo and su to run a command as any user.

crts · 05-21-2011, 08:47 AM

Quote:

Originally Posted by carltm

Well, technically sudo isn't the command to switch to any user.

That is correct. The -i option, however, simulates a login shell. With an according modification of the sudoers file you can do anything that the "real" user could do.

Quote:

Sudo lets you run a single command with
the permissions of root. Of course you can use a combination
of sudo and su to run a command as any user.

From the manpage:

Code:

       -i [command]
                   The -i (simulate initial login) option runs the shell
                   specified in the passwd(5) entry of the target user as a
                   login shell.  This means that login-specific resource files
                   such as .profile or .login will be read by the shell.  If a
                   command is specified, it is passed to the shell for
                   execution.  Otherwise, an interactive shell is executed.
                   sudo attempts to change to that user's home directory
                   before running the shell.  It also initializes the
                   environment, leaving DISPLAY and TERM unchanged, setting
                   HOME, MAIL, SHELL, USER, LOGNAME, and PATH, as well as the
                   contents of /etc/environment on Linux and AIX systems.  All
                   other environment variables are removed.
...
       -u user     The -u (user) option causes sudo to run the specified
                   command as a user other than root.  To specify a uid
                   instead of a user name, use #uid.  When running commands as
                   a uid, many shells require that the '#' be escaped with a
                   backslash ('\').  Note that if the targetpw Defaults option
                   is set (see sudoers(5)) it is not possible to run commands
                   with a uid not listed in the password database.

So, if I understand correctly, the 'sudo su' construct is not required to "switch" to another user.

Chirel · 05-21-2011, 09:31 AM

Hi,

I think like crts that your instructor have a solution based on chroot.

Just go read and learn how to do it.

adash · 05-21-2011, 10:35 AM

Yeah it's homework ( a project ) it's really 1/100 of this project. It's just a beggining and I'm stuck because I don't know some basis.

This project is to create a "virtual network" meaning a tree of directories (as virtual machines) and files to manage users etc.
I need to elaborate a command 'connect' in 2 modes user and admin.

Admin will have bunch of separated commands to create a new user, new machine etc.

User will be able to connect virtually to a machine (phisically just a name of a user will be added to machine/logged_users.txt)

The thing is I cannot start developping all the rest of the project (commands for admin and user) if I don't know how to make a login thing.