autoconf-2.13: 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/autoconf-2.13 - from package: autoconf213

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

Error in other languages:
autoconf-2.13: bevel nie gevind nie
autoconf-2.13: comandă negăsită
autoconf-2.13: comando não encontrado
autoconf-2.13: commande introuvable
autoconf-2.13: command not found
autoconf-2.13: käsku ei ole
autoconf-2.13: không tìm thấy lệnh
autoconf-2.13: komanda nerasta
autoconf-2.13: Kommando nicht gefunden.
autoconf-2.13: kommandot finns inte
autoconf-2.13: komut yok
autoconf-2.13: nie znaleziono polecenia
autoconf-2.13: níor aimsíodh an t-ordú
autoconf-2.13: no se encontró la orden
autoconf-2.13: no s'ha trobat l'ordre
autoconf-2.13: opdracht niet gevonden
autoconf-2.13: parancs nem található
autoconf-2.13: perintah tidak ditemukan
autoconf-2.13: príkaz nenájdený
autoconf-2.13: příkaz nenalezen
autoconf-2.13: команда не найдена
autoconf-2.13: командата не е открита
autoconf-2.13: 命令找不到
autoconf-2.13: コマンドが見つかりません