osd_clock: 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/osd_clock - from package: osdclock

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

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