concordance: 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/concordance - from package: concordance

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

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