tailf: 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/tailf - from package: util-linux-ng

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

On Debian possible default full paths are:

/bin/tailf - from package: util-linux

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

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