ttylog: 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/lib/debug/usr/sbin/ttylog - from package: ttylog-dbg
/usr/sbin/ttylog - from package: ttylog

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

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