xpp_blink: 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/sbin/xpp_blink - from package: dahdi-tools

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

On Debian possible default full paths are:

/usr/sbin/xpp_blink - from package: dahdi

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

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