v.patch: 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/lib64/grass-6.4.4/bin/v.patch - 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/v.patch - from package: grass-core

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

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