pymvpa2-prep-fmri: 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

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/pymvpa2-prep-fmri - from package: python-mvpa2

You may install the required package with command apt-get install {package}
Error in other languages:
pymvpa2-prep-fmri: bevel nie gevind nie
pymvpa2-prep-fmri: comandă negăsită
pymvpa2-prep-fmri: comando não encontrado
pymvpa2-prep-fmri: commande introuvable
pymvpa2-prep-fmri: command not found
pymvpa2-prep-fmri: käsku ei ole
pymvpa2-prep-fmri: không tìm thấy lệnh
pymvpa2-prep-fmri: komanda nerasta
pymvpa2-prep-fmri: Kommando nicht gefunden.
pymvpa2-prep-fmri: kommandot finns inte
pymvpa2-prep-fmri: komut yok
pymvpa2-prep-fmri: nie znaleziono polecenia
pymvpa2-prep-fmri: níor aimsíodh an t-ordú
pymvpa2-prep-fmri: no se encontró la orden
pymvpa2-prep-fmri: no s'ha trobat l'ordre
pymvpa2-prep-fmri: opdracht niet gevonden
pymvpa2-prep-fmri: parancs nem található
pymvpa2-prep-fmri: perintah tidak ditemukan
pymvpa2-prep-fmri: príkaz nenájdený
pymvpa2-prep-fmri: příkaz nenalezen
pymvpa2-prep-fmri: команда не найдена
pymvpa2-prep-fmri: командата не е открита
pymvpa2-prep-fmri: 命令找不到
pymvpa2-prep-fmri: コマンドが見つかりません