gl-system-install: 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/gl-system-install - from package: gitolite

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

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