The user 'sync' and 'shutdown'

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Operating Systems Linux Fedora The user 'sync' and 'shutdown'
# 8  
Old 09-26-2011
Originally Posted by vistastar
Is this a privilege control method that let some non-root users can shutdown the system using the 'shutdonw' user's password?
Originally Posted by Corona688
Perhaps it's because the 'shutdown' user belongs to the root group(group 0)?
On my fedora15 any non-root user can shutdown the system, why? The shutdown command is a soft link to consolehelper command.
What are the permissions on consolehelper?
Also, there is a /sbin/shutdown.
As opposed to what?
# 9  
Old 09-27-2011
[alien@fedora~]:)ls -l /sbin/shutdown
lrwxrwxrwx. 1 root root 16  9月  5 20:40 /sbin/shutdown -> ../bin/systemctl
[alien@fedora~]:)ls -l /bin/systemctl
-rwxr-xr-x. 1 root root 165632  4月 30 10:51 /bin/systemctl
lrwxrwxrwx. 1 root root 13  9月  5 20:40 /usr/bin/poweroff -> consolehelper
[alien@fedora~]:(ls -l /usr/bin/poweroff
lrwxrwxrwx. 1 root root 13  9月  5 20:40 /usr/bin/poweroff -> consolehelper
[alien@fedora~]:)ls -l /usr/bin/reboot
lrwxrwxrwx. 1 root root 13  9月  5 20:40 /usr/bin/reboot -> consolehelper
[alien@fedora~]:)ls -l /usr/bin/consolehelper
-rwxr-xr-x. 1 root root 6488  4月  1 05:24 /usr/bin/consolehelper

PS: the user 'shutdown' is not in any group.
# 10  
Old 09-30-2011
first google hit for 'man consolehelper':

consolehelper(8) - Linux man page
consolehelper - A wrapper that helps console users run system programs
progname [ options ]
consolehelper is a tool that makes it easy for console users to run system programs, doing authentication via PAM (which can be set up to trust all console users or to ask for a password at the system administrator's discretion). When possible, the authentication is done graphically; otherwise, it is done within the text console from which consolehelper was started.

It is intended to be completely transparent. This means that the user will never run the consolehelper program directly. Instead, programs like /sbin/shutdown are paired with a link from /usr/bin/shutdown to /usr/bin/consolehelper. Then when non-root users (specifically, users without /sbin in their path, or /sbin after /usr/bin) call the "shutdown" program, consolehelper will be invoked to authenticate the action and then invoke /sbin/shutdown. (consolehelper itself has no priviledges; it calls the userhelper(8) program do the real work.)

consolehelper requires that a PAM configuration for every managed program exist. So to make /sbin/foo or /usr/sbin/foo managed, you need to create a link from /usr/bin/foo to /usr/bin/consolehelper and create the file /etc/pam.d/foo, normally using the pam_console(8) PAM module.
So it uses special PAM settings to decide who's allowed to shutdown and so forth.

This is a Redhat-specific thing.
# 11  
Old 10-01-2011
Thank you very much.
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