coherence: 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/coherence - from package: python-Coherence

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

On Debian possible default full paths are:

/usr/bin/coherence - from package: python-Coherence

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

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