mnemosyne-blog: 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/mnemosyne-blog - from package: mnemosyne-blog

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