fld: command not found

Have You tried accessing the binary with the full path?

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/fld - from package: kon2

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