set_show_service: 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/set_show_service - from package: gnustep-gui

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

On Debian possible default full paths are:

/usr/bin/set_show_service - from package: gnustep-gui-runtime

You may install the required package with command apt-get install {package}

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