On this Linux 101, Jack Wallen explains the SUID permission bit.
In case you’re new to Linux administration, you have most likely already began studying about file permissions. If I mentioned “drwxrwxr-x,” you’d know what that meant. It is easy: A listing with proprietor and group learn, write, execute permissions, however solely learn and execute permissions for everybody else.
That is not the be-all, finish all for permissions. There are literally three extra permissions, certainly one of which I will educate you about proper now. Mentioned permission is named SUID, which stands for Set proprietor Person ID. It is a particular permission that applies to scripts or functions. If the SUID bit is about, when the command is run, it is efficient UID turns into that of the proprietor of the file, as an alternative of the consumer operating it.
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That is used to supply non permanent elevated permissions throughout execution. For instance, if the file being executed was owned by root and has the SUID bit set, irrespective of who’s operating the script or utility, the permissions would all the time (briefly) equal these of root.
One very easy-to-understand instance of that is when a consumer needs to vary their password they usually difficulty the sudo passwd command. If the SUID bit wasn’t set on passwd, the command can be run with out elevated privileges, and would not be capable of write to the required recordsdata to vary the password–hence the SUID bit.
In case you create a script (owned by the basis consumer) that wants the SUID bit set, you’d achieve this like:
sudo chmod u+s filename
The place filename is the title of the script or utility. As soon as the SUID bit is about, anytime that utility is executed, will probably be executed with briefly elevated privileges.
And that is the gist of the SUID permission bit. It sounds extra difficult than it truly is. Though you may not use it daily, you will be glad you already know it, once you run right into a state of affairs the place it is clearly essential.
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