adiff: 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/adiff - from package: atool

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

On Debian possible default full paths are:

/usr/bin/adiff - from package: atool

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

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