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Old 04-23-2006, 04:35 AM   #1
draget
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Users and permissions


Hi,

I intend on having one user account that has minimal permissions which can be used for two things:

a. running apps using screen
b. acting as an account for vsftpd to use when running

I started by making an account by using useradd and passwd to set it up, but it would seem the new user is not allowed to use screen, I get an error saying "Cannot open your terminal '/dev/pts/0' - please check." How can I fix this? and is there anything else I should do to reduce the abilities of this account?



Thanks,


Tom
 
Old 04-23-2006, 08:44 AM   #2
pen8wen
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what exactly are you typing at the prompt?
is screen essential?
what is the root reason why are you doing this?
 
Old 04-24-2006, 07:08 AM   #3
draget
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screen is essential

I am typing screen ./sc_serv I need the shoutcast server to sit in a screen by itself.


Thanks,

Tom
 
Old 04-25-2006, 10:59 AM   #4
pen8wen
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why cant you just use an xterm and su to the other user?
you didn't answer my question about the root of your problem.
 
Old 04-29-2006, 04:41 PM   #5
pen8wen
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i'm not sure what you mean by "an account with minimal permissions". in linux/unix/etc users have user permissions. they can only have access to other things (in general) if they belong to groups. users and groups don't "get" permissions like in windoze land. files have access based on their mode, as in chmod (change mode). if an app or file has read/execute permissions, 755 for example (meaning "other" may read and execute that file (or decend the directory if the file is a directory), anybody can read/execute that file.

see man chmod, man ls (look for info on -l (ell) option)

as for using screen, i don't think it will buy you anything that simply using an addl xterm won't. if you want it on a particular virtual desktop, move it there or create it there. if you want that xterm to think you are a particular user, su otheruser.

clear?

Last edited by pen8wen; 04-29-2006 at 04:42 PM.
 
Old 04-29-2006, 05:26 PM   #6
ioerror
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Quote:
as for using screen, i don't think it will buy you anything that simply using an addl xterm won't
screen is very different from simply running an app in an xterm. You can detach it and log back in later, from another computer etc. Also, the program will not die if the X server crashes/exits.

Quote:
b. acting as an account for vsftpd to use when running
You shouldn't really be using the same account for running a server. Create a separate account for vsftpd.
 
Old 04-30-2006, 01:14 AM   #7
draget
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ioerror is right, that's why I wish to use screen.

Thanks, pen8wen for the info on how linux permissions work.

So any ideas as to why screen doesn't work as this other user?


Thanks,

Tom
 
Old 04-30-2006, 06:26 AM   #8
ioerror
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Quote:
"Cannot open your terminal '/dev/pts/0' - please check."
I assume you can use screen OK as your regular user, so this is probably some permissions problem, though exactly what is not immediately obvious. One useful thing to do is to run the program under strace, that will tell you what it's trying to do when it fails (well, presumably trying to open /dev/pts/0 but the error value from the kernel will give a specific reason why it can't).
 
Old 04-30-2006, 06:34 AM   #9
ioerror
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Oops, posted same msg twice, sorry. Damn firefox.

Last edited by ioerror; 04-30-2006 at 06:38 AM.
 
Old 04-30-2006, 06:56 AM   #10
jschiwal
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Quote:
"Cannot open your terminal '/dev/pts/0' - please check."
Log into the (pts/0) virtual terminal as your user and try again. There is an option to the bash shell that reduces the commands that can be run. It is something you might do in a chroot jail. If you create a user for this, you could create a custom .bash_login and .bashrc so you can control the paths and environment. If you make these files owned by root, and only readable by your user, this can prevent alteration by someone breaking into that account. However, since the directory is owned by this user, they can be deleted, unles you use the sticky-mode for this users directory.

Look in the info bash pages, in section 6.2 on the Restricted Bash Shell.
I think that in the /etc/password file you use "/bin/bash -r" as the users shell, that can restrict the user to using this shell.

Last edited by jschiwal; 04-30-2006 at 10:04 PM.
 
  


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