celeryd: 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/celeryd - from package: python-celery

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

On Debian possible default full paths are:

/usr/bin/celeryd - from package: python-celery-common

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

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