I am reading the book Linux kernel development, in chapter 5 "System Call Implementation" page 77 says
For example, capable(CAP_SYS_NICE) checks whether the caller has the ability to modify nice values of other processes. By default, the superuser possesses all capabilities and nonroot possesses none. For example, here is the reboot() system call. Note how its first step is ensuring that the calling process has the CAP_SYS_REBOOT . If that one conditional statement were removed, any process could reboot the system.
However, in my Debian Sid I can reboot my machine by using gnome or by executing /sbin/reboot without sudo or su. How is this possible?
Maybe with systemctl?
ls -l /sbin/reboot lrwxrwxrwx 1 root root 14 Jun 28 04:23 /sbin/reboot -> /bin/systemctl
EDIT: My user groups
[damian@xvz:~]$ groups damian sudo wireshark bumblebee
EDIT 2: systemctl permissions
[damian@xvz:~]$ ls -l /bin/systemctl -rwxr-xr-x 1 root root 626640 Jun 28 04:23 /bin/systemctl