halt: 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:

/sbin/halt - from package: upstart
/usr/bin/halt - from package: usermode

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

On Debian possible default full paths are:

/sbin/halt - from package: systemd-sysv
/sbin/halt - from package: sysvinit-core
/sbin/halt - from package: upstart
/usr/lib/klibc/bin/halt - from package: klibc-utils
/usr/sbin/halt - from package: molly-guard

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

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