fluid: 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/fluid - from package: fltk-fluid

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

On Debian possible default full paths are:

/usr/bin/fluid - from package: fluid

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

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