phc2sys: 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/phc2sys - from package: linuxptp

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

Error in other languages:
phc2sys: bevel nie gevind nie
phc2sys: comandă negăsită
phc2sys: comando não encontrado
phc2sys: commande introuvable
phc2sys: command not found
phc2sys: käsku ei ole
phc2sys: không tìm thấy lệnh
phc2sys: komanda nerasta
phc2sys: Kommando nicht gefunden.
phc2sys: kommandot finns inte
phc2sys: komut yok
phc2sys: nie znaleziono polecenia
phc2sys: níor aimsíodh an t-ordú
phc2sys: no se encontró la orden
phc2sys: no s'ha trobat l'ordre
phc2sys: opdracht niet gevonden
phc2sys: parancs nem található
phc2sys: perintah tidak ditemukan
phc2sys: príkaz nenájdený
phc2sys: příkaz nenalezen
phc2sys: команда не найдена
phc2sys: командата не е открита
phc2sys: 命令找不到
phc2sys: コマンドが見つかりません