System Notes Org

I came up with some flashcards based on commonly used redhat linux commands. Here is my working draft. RHCE -Flash-Cards These notes should be helpful to anyone working on Redhat Enterprise Linux (RHEL), or preparing for the RHCE exam. My RHCE Study Guide was hugely popular, but unfortunately it had some potential copyright issues. This group of flashcards has also been released as a quick study guide, or cheat sheet, and contains much of the same original study guide material, but with all proprietary information removed. This 3-page guide is listed as RHCE Flash Cards (condensed version) How These Slides Were Created These slides were produced using OpenOffice.org Impress. Created Slides Saved as html Copied contents of html between body tags to .page files. Used a bash shell script with sed, and awk to get the files to appear properly for webgen. See script here— html2page.html Ran webgen on the directory to generate .html Also .pdf files were saved from Openoffice.org Wri...

These RCHE study notes were designed to be brief reminders of what you should already be familiar with. This topic covers HTTP server configuration. One thing to be aware of when working with Apache and the 2.6 kernel is SELinux. Overview of SELinux SELinux, is a Mandatory Access Control (MAC) security system for Linux based on the domain-type model. It was written by the NSA ( http://www.nsa.gov/selinux/ ) and is comprised of a kernel module (included in all 2.6 kernels), patches to certain security related applications, and a security policy. More info: http://www.redhat.com/magazine/001nov04/features/selinux/ Study Notes Here are the brief steps from my RHCE study guide to help you remember the steps to configure a virtual host, and configure permissions. * HTTP/HTTPS install httpd, check context with ls -Z   Q: Create a virtual host www1.example.com w/ subdirectory /var/www/html/www1   A:    1) install httpd, modify /etc/httpd/conf/httpd.conf file  ...

In Linux, directories are not accessible until the device is mounted. This is usually done at startup by the mount command which uses the /etc/fstab file. Files that start with a dot "." are hidden, but not completely (you can do ls -a to see the files). An example is the ~/.bashrc file. You can also hide files in a directory name that starts with a dot, e.g. ~/.ssh Now for the real trick Entire directories can be hidden, simply by mounting another device on top of the directory. The original files will still be in tact, but not visible until the device is remounted. First, find a device that is available to mount (boot is nice, because it is usually small). $ mount /dev/hda1 on /boot type ext3 (rw) ... etc... Then make your stealth directory, copy files to it, and mount a directory over it. $ cd /mnt $ mkdir stealth $ touch /mnt/stealth/somefile.txt $ ls /mnt/stealth/ somefile.txt $ mount -t ext3 /dev/hda1 /mnt/stealth ls /mnt/stealth/ config-2....

IP Forwarding Effectively makes a Linux box act as a router Is usually used with two network interfaces (one internal, and one external) Can be used with firewall services and is often used for NAT Steps to Turn on IP Forwarding  1) Modify /etc/sysctl.conf      vi /etc/sysctl.conf      add this line:      inet.ipv4.ip_forward=1  2) Make the Change Active      sysctl -p  3) To View Current Settings:      sysctl -a | grep ipv4 More info can be found on the redhat site: https://www.redhat.com/docs/manuals/enterprise/RHEL-4-Manual/security-guide/s1-firewall-ipt-fwd.html We'll leave firewall rules for another topic... rhce linux

This procedure assumes you have console access, and are authorized to make changes to accounts on the machine, including root. If you own the machine, you can boot into single user mode, and change the password, or create an account. If using grub (you should see a blue bootup screen), press "a", "space", "1", "enter" a 1 That will boot to single user mode. Then you can change the root password passwd Then reboot Ctrl-Alt-Del You should create user accounts other than root. Use the useradd command. useradd someone passwd someone rhce linux

Study notes for any exam are difficult enough to find, but RHCE material seems even more scarce. This article tells how to prepare for one of the objectives, which is configuration of an SMTP server. RHCE Study Notes I wrote up some study notes as I was preparing for the RCHE exam. Here are some quick notes based on the official RedHat objectives , labs, and possible questions I thought might be reasonable requests. SMTP Related Questions install sendmail, sendmail-cf, sendmail-doc (optional) Q: Configure mail server to accept internet email A: modify /etc/mail/sendmail.mc 1) cd /etc/mail 2) vi /etc/mail/sendmail.mc search for 127.0, put dnl at the front of the line 3) make or m4 sendmail.mc > sendmail.cf service sendmail restart Q: Mail alias A: modify /etc/aliases, run newaliases Q: Receive mail for DomainX.example.com A: modify sendmail mc as above, and add domain to /etc/mail/local-host-names ...

How Do I Configure Networking in RedHat Linux? Depending on the version of RedHat, or Fedora: redhat-config-network system-config-network bash-2.05b$ which redhat-config-network /usr/bin/redhat-config-network bash-2.05b$ Network Related Files: /etc/sysconfig/network-scripts/ifcfg-eth0 /etc/sysconfig/network /etc/hosts /etc/resolv.conf For more details, remember that the Red Hat Manuals are available online: http://www.redhat.com/docs/manuals Network Info: http://www.redhat.com/docs/manuals/enterprise/RHEL-4-Manual/ref-guide/s1-networkscripts-interfaces.html rhce linux