mason: 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/mason - from package: perl-HTML-Mason

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

On Debian possible default full paths are:

/usr/bin/mason - from package: mason
/usr/lib/seqan/bin/mason - from package: seqan-apps

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

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