Here is some sample output of these commands on sbsa.helpsystems.com (bold is emphasis):

 

[Skybot@sbsa scheduler]$ lsb_release -a

LSB Version:    :core-4.0-amd64:core-4.0-ia32:core-4.0-noarch:graphics-4.0-amd64:graphics-4.0-ia32:graphics-4.0-noarch:printing-4.0-amd64:printing-4.0-ia32:printing-4.0-noarch

Distributor ID: CentOS

Description:    CentOS release 5.6 (Final)

Release:        5.6

Codename:       Final

 

[Skybot@sbsa scheduler]$ uname -a

Linux sbsa.helpsystems.com 2.6.18-238.9.1.el5xen #1 SMP Tue Apr 12 18:53:56 EDT 2011 x86_64 x86_64 x86_64 GNU/Linux

 

[Skybot@sbsa scheduler]$ free -m -o

         total       used       free     shared    buffers     cached

Mem:          3551       2418       1132          0        256       1044

Swap:         8095          0       8095

 

[Skybot@sbsa scheduler]$ df -h

Filesystem            Size  Used Avail Use% Mounted on

/dev/mapper/ddf1_4c5349202020202080862925000000004711471100001450p1

                      441G  6.5G  412G   2% /

tmpfs                 1.8G     0  1.8G   0% /dev/shm

none                  1.8G   40K  1.8G   1% /var/lib/xenstored

 

 

From this output you can tell that sbsa is running CentOS 5.6 for x86_64 architecture (64-bit).  It has 3551MB of RAM and there are ~412GB free on the root drive of the system.

 

Note that these commands are not necessarily available on AIX, Solaris, or HP/UX in these exact forms.