estimate_observation_richness.py: 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/lib/qiime/bin/estimate_observation_richness.py - from package: qiime

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

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