xfmconcat: 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/xfmconcat - from package: minc-tools

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

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