yara: 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/yara - from package: yara

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

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