about: 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/share/redmine/bin/about - from package: redmine

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

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