chgrp: 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:

/bin/chgrp - from package: coreutils

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

On Debian possible default full paths are:

/bin/chgrp - from package: coreutils

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

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