ncrename: 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/bin/ncrename - from package: nco

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

On Debian possible default full paths are:

/usr/bin/ncrename - from package: nco

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

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