my-default-printer: 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/my-default-printer - from package: system-config-printer

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

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