virt-copy-in: 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-copy-in - 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-copy-in - from package: libguestfs-tools

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

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