idevicename: 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/idevicename - from package: libimobiledevice-utils

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

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