piv-tool: 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/piv-tool - from package: opensc

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

On Debian possible default full paths are:

/usr/bin/piv-tool - from package: opensc

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

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