Here’s the command to check if the system needs a reboot after running yum update.
Must be root or run it sudo.
$ needs-restarting -r ; echo $? Core libraries or services have been updated: openssl-libs -> 1:1.0.2k-21.el7_9 kernel -> 3.10.0-1160.31.1.el7 dbus -> 1:1.10.24-15.el7 linux-firmware -> 20200421-80.git78c0348.el7_9 glibc -> 2.17-324.el7_9 systemd -> 219-78.el7_9.3 Reboot is required to ensure that your system benefits from these updates. More information: https://access.redhat.com/solutions/27943 1
In this instance, it requires a reboot due to a new kernel.