qlogin: 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/bin/qlogin - from package: gridengine
/usr/share/gridengine/bin/lx26-amd64/qlogin - from package: gridengine
/usr/share/gridengine/bin/lx26-x86/qlogin - from package: gridengine

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

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