tsk_loaddb: 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/tsk_loaddb - from package: sleuthkit

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

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