tachyon: 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/tachyon - from package: tachyon

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

On Debian possible default full paths are:

/usr/bin/tachyon - from package: tachyon

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

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