sudo: yum: команда не найдена
After simple checks I've asked you in answer comment:
[root@Backup yum.repos.d]# yum
-bash: yum: command not found
[root@Backup yum.repos.d]# which yum
/usr/bin/which: no yum in (/usr/kerberos/sbin:/usr/kerberos/bin:/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/usr/X11R6/bin:/root/bin)
[root@Backup yum.repos.d]# echo $PATH
/usr/kerberos/sbin:/usr/kerberos/bin:/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/usr/X11R6/bin:/root/bin
[root@Backup yum.repos.d]# rpm -q yum
package yum is not installed
we can verify that you don't have yum installed in your system.
Please install it via rpm and you'll be able to launch it.
Santino