crm_diff: 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/crm_diff - from package: pacemaker-cli

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

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