fvwm-bug: 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/fvwm-bug - from package: fvwm

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

On Debian possible default full paths are:

/usr/bin/fvwm-bug - from package: fvwm

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

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