dhcpcd.sh: 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/share/rear/skel/default/bin/dhcpcd.sh - from package: rear

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

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