guestfish: 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/guestfish - 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/guestfish - from package: libguestfs-tools

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

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