pam-panel-icon: 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/pam-panel-icon - from package: usermode-gtk

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

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