Linux Permissions SUID, SGID and Sticky Bit Concept Explained with Examples
Linux Permissions SUID, SGID and Sticky Bit Concept Explained with Examples:
SUID (Super User ID)
SUID Stands for Super User ID. We know that root is the Super User in Linux and have all the rights to do administrative tasks but have you noticed that normal user also can do some administrative tasks such as reset the Password and as we know that by resetting the password two files getting updated i.e. /etc/passwd and /etc/shadow which is only can be done by root user. Let’s take another example i.e. Normal user can use the ping command to check network connectivity. Now let’s Understand what is the use of SUID. First of all, SUID should be applied to a binary file or to a script and we can apply SUID from root user only using the chmod command. We are applying SUID to any binary file or script means we are allowing that binary file to execute in any logged in user as an owner of that file. Means if i run the ping command by logging in with a normal user i.e. user1 still it will run as the root user only. Let’s take an example to understand the concept properly. SUID alphabetically identified by letter “s” and Numerically Identified by “4“.
Logging as a normal user i.e. user1 and try to use the ping command to check the connectivity.
[user1@localhost ~]$ whoami # To check currently Logged in User
user1
[user1@localhost ~]$ ping -c 3 localhost
PING localhost (127.0.0.1) 56(84) bytes of data.
64 bytes from localhost (127.0.0.1): icmp_seq=1 ttl=64 time=0.027 ms
64 bytes from localhost (127.0.0.1): icmp_seq=2 ttl=64 time=0.042 ms
64 bytes from localhost (127.0.0.1): icmp_seq=3 ttl=64 time=0.042 ms
--- localhost ping statistics ---
3 packets transmitted, 3 received, 0% packet loss, time 2000ms
rtt min/avg/max/mdev = 0.027/0.037/0.042/0.007 ms
# nmcli d
DEVICE TYPE STATE CONNECTION
eth0 ethernet 接続済み System eth0
virbr0 bridge 接続済み virbr0
eth1 ethernet 切断済み --
lo loopback 管理無し --
virbr0-nic tun 管理無し --
# nmcli d
DEVICE TYPE STATE CONNECTION
eth0 ethernet 接続済み System eth0
eth1 ethernet 接続済み Ethernet 接続 1
virbr0 bridge 接続済み virbr0
lo loopback 管理無し --
virbr0-nic tun 管理無し --
