sparkline: 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/sparkline - from package: python-sparklines

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

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