pgpring: 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/pgpring - from package: mutt

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

On Debian possible default full paths are:

/usr/bin/pgpring - from package: signing-party

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

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