authorindex: 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 Debian possible default full paths are:

/usr/bin/authorindex - from package: texlive-latex-extra

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

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