dnssec-trigger: 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/dnssec-trigger - from package: dnssec-trigger

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

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