pbs_server: command not found

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/sbin/pbs_server - from package: torque-server

You may install the required package with command yum install {package}

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