Problem with SCREEN

Soujiro · 06-10-2004, 10:44 PM

I have a dedicated server on the east coast, and i connect to it via SSH. I run game servers on it.

I cant run this program on screen, my screen works with my game servers, but i have this program called HLTV. When i start hltv with ./hltv, it works perfect. But i cant use screen with it.

I went into the proper directory and I typed:

Screen -A -m -d -S ./hltv

I did this with a NON root user on SSH and it said:

Must run suid root for multiuser support.

So i figured u cant do it on a nonuser, so i went into ROOT and did the same thing, and i got THIS msg:

Cannot identify account '.'.

I dont know what is wrong, plz help.

Thanks,
Chris

motub · 06-11-2004, 01:13 AM

Quote:

Must run suid root for multiuser support.

OK, as a non-root user, you get a message to do something, as root you get a message that the command is malformed.

I would suggest you take the first option and set the sticky bit on whatever needs it (not sure if the message refers to screen or hltv, or even ssh itself).

The first error is telling you that there is a permissions error, but it can be fixed.

Quote:

In addition to the basic file access modes (read, write, and execute), there are also a few special purpose modes. The special mode discussed in this week's tip is SUID, or set user ID.

If a file (command) is an executable and has the SUID bit set, the process running the command inherits the privileges and access rights of the file's owner for its duration, not those of the user who created the process. A frequently used UNIX command that exhibits this configuration is the passwd command:

-r-sr-sr-x 3 root sys 73748 Nov 2 2001 /usr/bin/passwd

The "s" in the third position of the owner permission set indicates set user ID and execute permission. Non-privileged users running passwd need this level of access (root) because the access-restricted /etc/shadow file has to be updated each time a login password is changed. Notice the ownership and permissions for this file:

-r-------- 1 root sys 346 Aug 16 15:14 /etc/shadow

If passwd was ran without having root's access rights, a non-privileged user would be unable to update /etc/shadow.

Just like basic file access modes, the SUID bit is also set with the chmod command. Consider the starting access mode of unixprogram:

-r-xr-xr-x 1 root other 647 Sep 6 16:17 unixprogram

The following command will set the SUID bit for this file:

# chmod 4555 unixprogram
# ls -l unixprogram
-r-sr-xr-x 1 root other 647 Sep 6 16:17 unixprogram

As you can see, the "x" in the owner permission set was changed to "s". Review chmod's man page for more information regarding the setting of this special permission.

It is important to recognize that using this functionality may also introduce security vulnerabilities, especially if used with files owned by root. This becomes even more of a concern if the files are shell scripts because of the relative ease in which they can be exploited.

(from Special Purpose Access Modes (Permissions) - Part I - SUID (set user ID).)

The SUID bit is also called the "sticky bit" (as the bit "sticks" to the file, no matter how conditions the file is being used under may change).

So if you set the sticky bit on the program that's asking for it to be set, you should be able to run that command as a non-root user.

Hope this helps.

Soujiro · 06-11-2004, 12:09 PM

Wait i solved it, i forgot to add a name for the -S command :P

screen -A -m -d - S hltv ./hltv

Thanks anyway for the huge msg motub.

2fishandchips · 08-28-2013, 03:39 AM

Had the same problem using screen with option -dm only
This worked for me.
screen -dm bash -c "./temp.sh"