Add note OS

doc.zih.tu-dresden.de/docs/jobs_and_resources/hardware_overview.md

@@ -140,6 +140,8 @@ CPUs.
     - 512 GB RAM
 - Hostnames: `n[1001-1630].barnard.hpc.tu-dresden.de`
 - Login nodes: `login[1-4].barnard.hpc.tu-dresden.de`
+- Operating system: Red Hat Enterpise Linux 8.7
+- Further information on the usage is documented on the site [CPU Cluster Barnard](barnard.md)
 
 ## Alpha Centauri
 
@@ -153,6 +155,7 @@ and is designed for AI and ML tasks.
     - 3.5 TB local memory on NVMe device at `/tmp`
 - Hostnames: `i[8001-8037].alpha.hpc.tu-dresden.de`
 - Login nodes: `login[1-2].alpha.hpc.tu-dresden.de`
+- Operating system: Rocky Linux 8.7
 - Further information on the usage is documented on the site [GPU Cluster Alpha Centauri](alpha_centauri.md)
 
 ??? note "Maintenance from November 27 to December 12"