xfmflip: 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/xfmflip - from package: minc-tools

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

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