ethumbd: 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/ethumbd - from package: libethumb-client-bin

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