img_stat: command not found

Have You tried accessing the binary with the full path?

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 Debian possible default full paths are:

/usr/bin/img_stat - from package: sleuthkit

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