qemu-system-sh4: 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-sh4 - from package: qemu-system-misc

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

Error in other languages:
qemu-system-sh4: bevel nie gevind nie
qemu-system-sh4: comandă negăsită
qemu-system-sh4: comando não encontrado
qemu-system-sh4: commande introuvable
qemu-system-sh4: command not found
qemu-system-sh4: käsku ei ole
qemu-system-sh4: không tìm thấy lệnh
qemu-system-sh4: komanda nerasta
qemu-system-sh4: Kommando nicht gefunden.
qemu-system-sh4: kommandot finns inte
qemu-system-sh4: komut yok
qemu-system-sh4: nie znaleziono polecenia
qemu-system-sh4: níor aimsíodh an t-ordú
qemu-system-sh4: no se encontró la orden
qemu-system-sh4: no s'ha trobat l'ordre
qemu-system-sh4: opdracht niet gevonden
qemu-system-sh4: parancs nem található
qemu-system-sh4: perintah tidak ditemukan
qemu-system-sh4: príkaz nenájdený
qemu-system-sh4: příkaz nenalezen
qemu-system-sh4: команда не найдена
qemu-system-sh4: командата не е открита
qemu-system-sh4: 命令找不到
qemu-system-sh4: コマンドが見つかりません