host: 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/host - from package: bind-utils

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

On Debian possible default full paths are:

/usr/bin/host - from package: bind9-host
/usr/bin/host - from package: knot-host

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

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