xmgrace: 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/xmgrace - from package: grace

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

On Debian possible default full paths are:

/usr/bin/xmgrace - from package: grace

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

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