cairo-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/cairo-clock - from package: cairo-clock

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

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