fastasort: 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/fastasort - from package: exonerate

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

On Debian possible default full paths are:

/usr/bin/fastasort - from package: exonerate

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

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