lsdnssec: 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/lsdnssec - from package: dnssec-tools

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

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