ylistb: command not found

Have You tried accessing the binary with the full path?

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/ylistb - from package: patchy

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