cas-admin: command not found

Have You tried accessing the binary with the full path?

Maybe Your $PATH variable doesn't contain the default paths? echo $PATH should give something like:

[root@server ~]# echo $PATH
/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin

If it's empty, You may set the PATH variable with this command

export PATH="/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin"

On CentOS possible default full paths are:

/usr/bin/cas-admin - from package: cas

You may install the required package with command yum install {package}
Error in other languages:
cas-admin: bevel nie gevind nie
cas-admin: comandă negăsită
cas-admin: comando não encontrado
cas-admin: commande introuvable
cas-admin: command not found
cas-admin: käsku ei ole
cas-admin: không tìm thấy lệnh
cas-admin: komanda nerasta
cas-admin: Kommando nicht gefunden.
cas-admin: kommandot finns inte
cas-admin: komut yok
cas-admin: nie znaleziono polecenia
cas-admin: níor aimsíodh an t-ordú
cas-admin: no se encontró la orden
cas-admin: no s'ha trobat l'ordre
cas-admin: opdracht niet gevonden
cas-admin: parancs nem található
cas-admin: perintah tidak ditemukan
cas-admin: príkaz nenájdený
cas-admin: příkaz nenalezen
cas-admin: команда не найдена
cas-admin: командата не е открита
cas-admin: 命令找不到
cas-admin: コマンドが見つかりません