pinentry-gtk-2: 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/pinentry-gtk-2 - from package: pinentry-gtk

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

On Debian possible default full paths are:

/usr/bin/pinentry-gtk-2 - from package: pinentry-gtk2

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

Error in other languages:
pinentry-gtk-2: bevel nie gevind nie
pinentry-gtk-2: comandă negăsită
pinentry-gtk-2: comando não encontrado
pinentry-gtk-2: commande introuvable
pinentry-gtk-2: command not found
pinentry-gtk-2: käsku ei ole
pinentry-gtk-2: không tìm thấy lệnh
pinentry-gtk-2: komanda nerasta
pinentry-gtk-2: Kommando nicht gefunden.
pinentry-gtk-2: kommandot finns inte
pinentry-gtk-2: komut yok
pinentry-gtk-2: nie znaleziono polecenia
pinentry-gtk-2: níor aimsíodh an t-ordú
pinentry-gtk-2: no se encontró la orden
pinentry-gtk-2: no s'ha trobat l'ordre
pinentry-gtk-2: opdracht niet gevonden
pinentry-gtk-2: parancs nem található
pinentry-gtk-2: perintah tidak ditemukan
pinentry-gtk-2: príkaz nenájdený
pinentry-gtk-2: příkaz nenalezen
pinentry-gtk-2: команда не найдена
pinentry-gtk-2: командата не е открита
pinentry-gtk-2: 命令找不到
pinentry-gtk-2: コマンドが見つかりません