trean-backfill-favicons: 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/trean-backfill-favicons - from package: php-horde-trean

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

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