rb-archfix: 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/lib/mailman/bin/rb-archfix - from package: mailman

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

On Debian possible default full paths are:

/usr/lib/mailman/bin/rb-archfix - from package: mailman

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

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