dos2unix.sh: 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 CentOS possible default full paths are:

/usr/lib/python2.6/site-packages/askbot/bin/dos2unix.sh - from package: askbot

You may install the required package with command yum install {package}

Error in other languages:
dos2unix.sh: bevel nie gevind nie
dos2unix.sh: comandă negăsită
dos2unix.sh: comando não encontrado
dos2unix.sh: commande introuvable
dos2unix.sh: command not found
dos2unix.sh: käsku ei ole
dos2unix.sh: không tìm thấy lệnh
dos2unix.sh: komanda nerasta
dos2unix.sh: Kommando nicht gefunden.
dos2unix.sh: kommandot finns inte
dos2unix.sh: komut yok
dos2unix.sh: nie znaleziono polecenia
dos2unix.sh: níor aimsíodh an t-ordú
dos2unix.sh: no se encontró la orden
dos2unix.sh: no s'ha trobat l'ordre
dos2unix.sh: opdracht niet gevonden
dos2unix.sh: parancs nem található
dos2unix.sh: perintah tidak ditemukan
dos2unix.sh: príkaz nenájdený
dos2unix.sh: příkaz nenalezen
dos2unix.sh: команда не найдена
dos2unix.sh: командата не е открита
dos2unix.sh: 命令找不到
dos2unix.sh: コマンドが見つかりません