masai_mapper: 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 Debian possible default full paths are:

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

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

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