phc_ctl: 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/sbin/phc_ctl - from package: linuxptp

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

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