tail: 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/tail - from package: coreutils

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

On Debian possible default full paths are:

/usr/bin/tail - from package: coreutils
/usr/lib/plan9/bin/tail - from package: 9base

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

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