gimp: 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/gimp - from package: gimp

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

On Debian possible default full paths are:

/usr/bin/gimp - from package: gimp

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

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