Explanation:
Conclusions: 1. I find that it is common to add various service access limits in the exam RHCE. The exercises like: require one network segment can be accessed another network segments can not be accessed, the following are some conclusions for various service: tcp_wrappers:/etc/hosts.allow,/etc/hosts.deny tcp_wrappers can filter the TCP’s accessing service. TCP whether has the filtering function which depends on this service whether use the function library of tcp_wrappers, or this service whether has the xinetd process of starting function of tcp_wrappers. tcp_wrappers’s main configuration file is /etc/hosts.allow,/etc/ hosts.deny.And the priority of the documents in hosts. allow is higher than hosts. deny. Visit will be passed if no match was found.sshd,vsftpd can use the filtering service of tcp_wrappers. Configuration example: Notice: The two configuration files’ syntax can refer to hosts_access (5) and hosts_options(5) sshd_config There are four parameters in this configuration file: DenyUsers, AllowUsers, DenyGroups, AllowGroups, they are used to limit some users or user groups to proceed Remote Login through the SSH. These parameters’ priority level is DenyUsers->AllowUsers->DenyGroups->AllowGroups Configuration example: httpd Service Through the /etc/httpd/conf/httpd.conf in parameters, can add <Directory> to control the url access. Just as: Notice: So pay attention, deny’s and allow’s priority level in order deny,allow is: the backer has the higher priority level. But here, allow’s priority has a higher priority level. nfs Service nfs service directly control the visits through file /etc/exports, just as: samba Service Parameter hosts allow in /etc/samba/smb.conf which is used as Access Control, just as: 2. Paying attention to use Mount parameters: _netdev,defaults when you are mounting ISCSI disk. 3. Stop the NetworkManager /etc/init.d/NetworkManager stop chkconfig NetworkManager off 4. When you are deploying ifcfg-ethX, add parameters: PEERDNS=no 5. Empty the firewall in RHCSA RHCE、 : 6. Narrow lv steps: 7. Mount the using command - swap which is newly added in /etc/fstab 8. If Verification is not passed when you are installing software, can import public key: rpm import /etc/pki/rpm…/…release and so on. In yum.repo, you also can deploy gpgkey, for example, gpgkey=/etc/pki/rpm…/…release 9. When you are using “Find” command to search and keep these files, paying attention to use cp -a to copy files if you use user name and authority as your searching methods.