congruity: 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 Debian possible default full paths are:

/usr/bin/congruity - from package: congruity

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

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