viewmol: 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/viewmol - from package: viewmol

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

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