A guide to RHCSA & RHCE Certifications Luis M. Arranz L. Arranz, 2012 1/223 0. Introduction ............................................................................................................................... 10 1. RHCSA/RHCE Objectives ............................................................................................................ 11 1.1. RHCSA ................................................................................................................................. 11 1.2. RHCE ................................................................................................................................... 13 2. SysV Init Runlevels .................................................................................................................... 15 2.1. Runlevels ............................................................................................................................. 15 2.2. Changing Runlevels (the process of) ................................................................................... 16 2.3. Managing services scripts with ‘chkconfig’ command ........................................................... 16 2.4. Changing Runlevels at Boot Time ........................................................................................ 17 3. Shutting down and rebooting a system ..................................................................................... 17 3.1. Boot systems into different runlevels manually .................................................................... 18 4. Forgotten 'root' password / using single-user to gain access ..................................................... 19 5. Basic system recovery ............................................................................................................... 20 5.1. Booting into Rescue Mode ................................................................................................... 20 5.2. Booting into Single-User Mode ............................................................................................ 22 5.3. Booting into Emergency Mode ............................................................................................. 22 6. kdump: Config. kernel dumps & analyzing the crash dump ....................................................... 23 6.1. The kdump procedure ......................................................................................................... 25 6.2. Configuring crashkernel on RHEL6.0 and RHEL6.1 kernels .................................................. 25 6.3. Configuring crashkernel on RHEL6.2 (and later) kernels ...................................................... 26 7. Setting local hostname and domain name ................................................................................. 26 8. Users and Groups ...................................................................................................................... 27 8.1. Users and Groups management .......................................................................................... 27 8.1.1. Adding a user ...........................................................................................27 8.1.2. Adding a group ..........................................................................................27 8.1.3. Password aging .........................................................................................28 8.2. Standard users .................................................................................................................... 29 8.3. Standard groups .................................................................................................................. 29 8.4. User private groups ............................................................................................................. 30 8.4.1. Group directories .......................................................................................31 8.5. Shadow passwords .............................................................................................................. 31 8.6. Most relevant commands & files .......................................................................................... 32 8.7. User Accounts, Groups and permissions .............................................................................. 35 8.8. Create and configure set-GID directories for collaboration .................................................. 36 9. Authentication Configuration ..................................................................................................... 38 9.1. Tips for using authconfig ..................................................................................................... 38 9.2. Configuring LDAP User Stores ............................................................................................. 38 9.3. Configure a system to use an existing LDAP directory service ............................................. 38 9.4. Configuring NIS User Stores ................................................................................................ 39 9.5. Configuring Winbind User Stores ......................................................................................... 39 9.6. Configuring Kerberos Authentication ................................................................................... 40 L. Arranz, 2012 2/223 9.7. Configuring Local Authentication Settings ............................................................................ 42 9.8. Configuring Fingerprint Authentication ................................................................................ 42 9.9. Configuring Smart Card Authentication ................................................................................ 42 9.10. Managing Kickstart and Configuration Files ....................................................................... 42 9.11. Using Custom Home Directories ........................................................................................ 43 10. Building a chroot jail environment ........................................................................................... 44 11. Accessing remote systems via 'ssh' and VNC ........................................................................... 45 11.1. Configure key-based authentication .................................................................................. 45 11.2. Configure additional options described in documentation .................................................. 46 11.3. SSH quick configuration procedure (packages, SELinux, auto start, basic operation, host/user-based security) ........................................................................................................... 46 11.4. Connecting via 'ssh' ........................................................................................................... 47 11.5. Configure Virtual Network Computing (VNC) to work with RHEL ....................................... 47 11.6. etc/sysconfig/vncservers ................................................................................................... 49 11.7. How to tunnel VNC connections over 'ssh' ......................................................................... 49 12. Login or switch users to 'root' account ..................................................................................... 49 12.1. Why should one use "su" instead of login as 'root' ............................................................ 49 12.2. Allow a user to run commands as root ('sudo') .................................................................. 50 12.3. Restrict the use of 'su' command ....................................................................................... 51 12.4. Using 'su' command........................................................................................................... 51 12.5. Differences between "su -" and "su" .................................................................................. 52 13. Access Control Lists (ACL) ....................................................................................................... 52 13.1. Mounting File Systems ....................................................................................................... 52 13.1.1. NFS ......................................................................................................53 13.2. Setting Access ACLs ........................................................................................................... 53 13.3. Setting Default ACLs .......................................................................................................... 54 13.4. Retrieving ACLs ................................................................................................................. 54 13.5. Archiving File Systems with ACLs ....................................................................................... 55 13.6. Compatibility with older systems ....................................................................................... 56 14. Locating and analyzing system logs files .................................................................................. 56 14.1. Configure a system to log to a remote system .................................................................. 57 14.2. Configure a system to accept logging from a remote system ............................................ 57 15. Managing system resources ....................................................................................................