g_gyrate: 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/g_gyrate - from package: gromacs

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

On Debian possible default full paths are:

/usr/bin/g_gyrate - from package: gromacs

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

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