isnsadm: 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/isnsadm - from package: isns-utils

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

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