jpeg_extract: 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 Debian possible default full paths are:

/usr/bin/jpeg_extract - from package: sleuthkit

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

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