fastachecksum: 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/fastachecksum - from package: exonerate

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

On Debian possible default full paths are:

/usr/bin/fastachecksum - from package: exonerate

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

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