To find the kernel version and memory details of LINUX / SOLARIS Operating System

In SOLARIS, uname -r will give you the solaris release level.
some other useful options with uname are

uname -s [Operating system]

uname -r [Release version]

For example if output is:

then it denotes:
* 2 : Kernel version
* 6 : The major revision of the kernel
* 22 : The minor revision of the kernel
* 14 : Immediate fixing / bug fixing for critical error
* generic : Distribution specific sting. For example, Redhat appends string such as EL5 to indicate RHEL 5 kernel.

uname -v
Generic_117350-27[OS version]

uname -a
SunOS hostname 5.8 Generic_117350-27 sun4u sparc
The last two words describes h/w name and processor respctl[equivalent to -m and -p),

$ cat /etc/redhat-release
Red Hat Enterprise Linux Server release 5 (Tikanga)
this command return the Centos version

To find the Memory details:

dmesg | grep ^Memory:

Output: Memory: 1734144k/1792092k available (2512k kernel code, 49156k reserved, 1396k data, 184k init)

The second value is the physical RAM size. It'll also tell you what other junk is subtracted from that to give you what you get with "free"..