glocktop: 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/glocktop - from package: gfs2-utils

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

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