lighttpd: 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/lighttpd - from package: lighttpd

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

On Debian possible default full paths are:

/usr/sbin/lighttpd - from package: lighttpd

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

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