ctdb_lock_helper: 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/ctdb_lock_helper - from package: ctdb

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

On Debian possible default full paths are:

/usr/bin/ctdb_lock_helper - from package: ctdb

You may install the required package with command apt-get install {package}

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