mstack: 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

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/mstack - from package: umview

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