Editing Setuid (section)

===When set on an executable file===

When the <code>setuid</code> or <code>setgid</code> attributes are set on an [[executable]] file, then any users able to execute the file will automatically execute the file with the privileges of the file's owner (commonly [[superuser|root]]) and/or the file's group, depending upon the flags set.<ref name="oreilly" /> This allows the system designer to permit trusted programs to be run which a user would otherwise not be allowed to execute. These may not always be obvious. For example, the [[ping (networking utility)|ping]] command may need access to networking privileges that a normal user cannot access; therefore it may be given the setuid flag to ensure that a user who needs to ping another system can do so, even if their account does not have the required privilege for sending packets.

==== Security impact====
For security purposes, the invoking user is usually prohibited by the system from altering the new process in any way, such as by using <code>[[ptrace]]</code>, <code>LD_LIBRARY_PATH</code> or sending signals to it, to exploit the raised privilege, although signals from the terminal will still be accepted.

While the <code>setuid</code> feature is very useful in many cases, its improper use can pose a security risk<ref name="oreilly" /> if the <code>setuid</code> attribute is assigned to [[executable]] programs that are not carefully designed. Due to potential security issues,<ref>{{cite web|url=http://www.faqs.org/faqs/unix-faq/faq/part4/section-7.html|title=Unix - Frequently Asked Questions}}</ref> many operating systems ignore the <code>setuid</code> attribute when applied to executable ''[[shell script]]s''.{{cn |date=March 2024}}

The presence of <code>setuid</code> executables explains why the <code>[[chroot]]</code> system call is not available to non-[[superuser|root]] users on Unix. See [[chroot#Limitations|limitations of <code>chroot</code>]] for more details.