varmon: 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/varmon - from package: varmon

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