startfluxbox: 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/startfluxbox - from package: fluxbox

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

On Debian possible default full paths are:

/usr/bin/startfluxbox - from package: fluxbox

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

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