SunOS is the core operating system comprising the kernel, utilities and basic libraries. Solaris is the broader environment comprising SunOS, OpenWindows and networking support. In other words, SunOS is a component of Solaris.
SunOS and Solaris relate to each other as follows:
For example, when one does a 'uname -a' or ‘uname –r’ this reports that the server has SunOS 5.6 installed which means that it actually got Solaris 2.6 installed which is a bit confusing and not as complete. If you're not into Solaris, it's easy to get confused by the fact that (for example) there's more than one version of Solaris 8, and it's also called Solaris 5.8 and even SunOS 5.8.
The following example shows the output for ‘uname’ command output:
We can also use more /etc/release to find out the Solaris version.
In addition, we can also run the command ‘showrev’. There's a man page on showrev and there are switches to help you do whatever you're trying to do. The following example shows the ‘showrev’ command output.
$ showrev –a
Kernel architecture: sun4u
Application architecture: sparc
Hardware provider: Sun_Microsystems
Kernel version: SunOS 5.9 May 2002
X11 Version 6.4.2 11 April 2001
No patches are installed
I think ‘showrev’ is the best.
Please note the Backup Exec SCL mentions the Solaris version and not the SunOS version. One can refer to the table below to compare the SunOS & the Solaris version.