g.list: 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/lib64/grass-6.4.4/bin/g.list - from package: grass

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

On Debian possible default full paths are:

/usr/lib/grass64/bin/g.list - from package: grass-core

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