dropwatch: 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 CentOS possible default full paths are:

/usr/bin/dropwatch - from package: dropwatch

You may install the required package with command yum install {package}

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