.arch-n-opsys: 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/lib/smlnj/bin/.arch-n-opsys - from package: smlnj-runtime

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