Advanced File Permission

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SUID

SUID stands for Set User ID. SUID allows applications to run by normal user with privileges of root user. That means in case I have an application (eg. ping) whose owner is 'root' and it has its SUID bit set, then when I run this application as a normal user, that application would still run as root. By default the SUID will be applied on ping so that the normal users will also can ping to other systems. 2

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Example

Comp1 192.168.0.1 Administrator

Comp3 192.168.0.3

Comp2 192.168.0.2

Comp4 192.168.0.4 4

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SUID commands

To Toremove removeSUID SUID [root@comp1 [root@comp1~]#chmod ~]#chmod 0755 0755 /bin/ping /bin/ping

To Toadd addSUID SUID [root@comp1 [root@comp1~]#chmod ~]#chmod 4755 4755 /bin/ping /bin/ping

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SGID

SGID

is

used

for

group

inheritance,

when

SGID is applied to a directory, all sub directories & files created by any user in that particular directory would be owned by the specified group, regardless of user s group.

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Sticky Bit

Sticky bit

is used to

restrict

others

from

removing the files/dir s. When applied only owner of that particular file/dir can delete them. Root / Superuser can also remove them, even if it is applied.

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