vipw: 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/vipw - from package: shadow-utils

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

On Debian possible default full paths are:

/usr/sbin/vipw - from package: passwd

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

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