initialize_github2fedmsg_db: command not found

Have You tried accessing the binary with the full path?

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/bin/initialize_github2fedmsg_db - from package: github2fedmsg

You may install the required package with command yum install {package}
Error in other languages:
initialize_github2fedmsg_db: bevel nie gevind nie
initialize_github2fedmsg_db: comandă negăsită
initialize_github2fedmsg_db: comando não encontrado
initialize_github2fedmsg_db: commande introuvable
initialize_github2fedmsg_db: command not found
initialize_github2fedmsg_db: käsku ei ole
initialize_github2fedmsg_db: không tìm thấy lệnh
initialize_github2fedmsg_db: komanda nerasta
initialize_github2fedmsg_db: Kommando nicht gefunden.
initialize_github2fedmsg_db: kommandot finns inte
initialize_github2fedmsg_db: komut yok
initialize_github2fedmsg_db: nie znaleziono polecenia
initialize_github2fedmsg_db: níor aimsíodh an t-ordú
initialize_github2fedmsg_db: no se encontró la orden
initialize_github2fedmsg_db: no s'ha trobat l'ordre
initialize_github2fedmsg_db: opdracht niet gevonden
initialize_github2fedmsg_db: parancs nem található
initialize_github2fedmsg_db: perintah tidak ditemukan
initialize_github2fedmsg_db: príkaz nenájdený
initialize_github2fedmsg_db: příkaz nenalezen
initialize_github2fedmsg_db: команда не найдена
initialize_github2fedmsg_db: командата не е открита
initialize_github2fedmsg_db: 命令找不到
initialize_github2fedmsg_db: コマンドが見つかりません