pcapinfo: 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/pcapinfo - from package: perl-Net-Pcap

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

On Debian possible default full paths are:

/usr/bin/pcapinfo - from package: libnet-pcap-perl

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

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