seahorse-agent: 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/seahorse-agent - from package: seahorse-plugins

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

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