qemu-system-arm: 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/qemu-system-arm - from package: qemu-system-arm

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

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