genreflex-rootcint: 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/genreflex-rootcint - from package: root-reflex

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

On Debian possible default full paths are:

/usr/bin/genreflex-rootcint - from package: libroot-core-dev

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

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