ikiwiki-mass-rebuild: 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/ikiwiki-mass-rebuild - from package: ikiwiki

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

On Debian possible default full paths are:

/usr/sbin/ikiwiki-mass-rebuild - from package: ikiwiki

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

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