fiu-ls: 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/fiu-ls - from package: fiu-utils

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

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