liferea: 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/liferea - from package: liferea

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

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