virt-cat: 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/virt-cat - from package: libguestfs-tools-c

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

On Debian possible default full paths are:

/usr/bin/virt-cat - from package: libguestfs-tools

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

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