vmixctl: 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/sbin/vmixctl - from package: oss4-base

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