Common Unix / Linux file permissions – quick reference

The most common permissions include:

400     r——–       files (won’t let you accidentally erase)

444     r–r–r–      files (lets everyone read)

600     rw——-     files (no one else can read or see files)

644     rw-r–r–      files (owner can read/write, group read, public read)

664     rw-rw-r–      files (owner can read/write, group read/write, public read)

666     rw-rw-rw-     files (owner can read/write, group read/write, public read/write)

700     rwx——          programs and directories (Owner r/w/execute)

750     rwxr-x—          programs and directories etc

755     rwxr-xr-x          programs and directories etc

777     rwxrwxrwx     programs and directories etc

 

Network upgrade for Ubuntu desktops

Here are some quick info for updating Ubuntu from the command line that I used earlier.

Network upgrade for Ubuntu desktops (Recommended)

You can easily upgrade over the network with the following procedure.

  1. Start System/Administration/Update Manager.
  2. Click the Check button to check for new updates.
  3. If there are any updates to install, use the Install Updates button to install them, and press Check again after that is complete.
  4. A message will appear informing you of the availability of the new release.
  5. Click Upgrade.
  6. Follow the on-screen instructions.

Network upgrade for Ubuntu servers (Recommended)

  1. Install update-manager-core if it is not already installed:
    sudo apt-get install update-manager-core
    
  2. edit /etc/update-manager/release-upgrades and set Prompt=normal
  3. Launch the upgrade tool:
    sudo do-release-upgrade
  4. Follow the on-screen instructions.

Upgrade from 8.04 LTS to 10.04 LTS

Network upgrade for Ubuntu desktops (Recommended)

You can easily upgrade over the network with the following procedure.

  1. Press Alt-F2 and type update-manager --devel-release
  2. Click the Check button to check for new updates.
  3. If there are any updates to install, use the Install Updates button to install them, and press Check again after that is complete.
  4. A message will appear informing you of the availability of the new release.
  5. Click Upgrade.
  6. Follow the on-screen instructions.

Network upgrade for Ubuntu servers (Recommended)

  1. Install update-manager-core if it is not already installed:
    sudo apt-get install update-manager-core
  2. edit /etc/update-manager/release-upgrades and set Prompt=lts
  3. Launch the upgrade tool:
    sudo do-release-upgrade --devel-release
  4. Follow the on-screen instructions.

Other upgrade options exist, please view the Upgrade Notes to learn more.

Something not to do lightly..

Simulating High Traffic

If your problem has to do with your memory usage spiking at certain times of the day, it can be hard to figure out what’s happening since things are often running well when you’re able to check on them. When that’s the case, it’s important to be able to simulate the environment that’s causing the problem. A great tool for this is the httperf command. This is a tool for UNIX-like operating systems that allows you to measure web server performance. This is a fairly complex tool that can do a lot, but the most simple usage would be something like this:

  httperf --hog --server=www.example.com --num-conns=1000 --rate=20 --timeout=5

That command will hit the supplied domain with 1000 connections at a rate of 20 connections per second. Connections that get no response within 5 seconds are dropped. The “–hog” parameter simply allows it to hog network ports on your system to allow for more outgoing connections. Depending on the amount of traffic you’re trying to simulate, you’ll need to adjust that.

So, to see what’s going on, you’ll likely want three terminal windows open. One will be SSH’d into your PS with top -c running sorted by memory (shift-m). Another will be SSH’d into your PS where you can repeatedly run free -m while httperf is running to monitor memory usage. And the third will be running httperf from your local machine (you do NOT want to run this from your PS itself).

This is great for profiling your sites and checking to see if caching is working. You can run this for each of your domains and see which ones affect your memory usage the most so you know where to focus your attention when working on optimizing things.

Another tool that can do something similar to this, but has fewer features is the Apache Benchmark tool. To use that you would use a command similar to this:

  ab -n 1000 -c 20 http://www.example.com

That would attempt to create 1000 connections to http://www.example.com limiting itself to 20 concurrent connections. Between both tools you should be able to get a good idea of what’s going on with your sites under higher traffic.

You can find links to get more information on httperf and Apache Benchmark in the #External Links section below.

Maverick Meerkat – Ubuntu 10.10 Release Schedule

seems i’m always the last to know…

Amber GranerTags:

Below is the Maverick Meerkat, Ubuntu 10.10 Release Schedule. Now you can mark your calendars and know when and where the milestones in the development cycle are. This should also allow Ubuntu users to keep an eye and ear open for all the wonderful and exciting things being developed. If you want to get involved in testing, or maybe you just want to download the Release Candidate prior to the final release. Now you can know what to expect and when. Should the schedule change I’ll correct here on You-In-Ubuntu as well.

Alpha 1 – June 3rd, 2010

Alpha 2 – July 1st, 2010

Alpha 3 – August 5th, 2010

Beta – September 2nd, 2010

Release Candidate – September 30th, 2010

Final Release – SUNDAY – October, 10, 2010

For more information on Ubuntu go to: http://www.ubuntu.com/

For more information on how you can participate in the Ubuntu Community got to: http://www.ubuntu.com/community

Please send your questions, comments, and suggestions to: amber [at] ubuntu-user [dot] com.

X11 forwarding and SSH for remote linux / ubuntu desktop

Here’s something I used earlier..

Connecting to Remote Linux Desktop via SSH with X11 Forwarding

by Forrest Sheng Bao http://fsbao.net

There are two advantages of Linux, compared with many other operating systems, such as Windows and Mac OS X. The first advantage is the ultimate B/S architecture. Thus, everything software is either a server or a program running on a server. When clicking my mouse, I am talking to a server program called X Server on my box. When surfing Internet, I am using Firefox, a browser running on X Server. The second advantage is that you can always find many choices to achieve one goal. When I wanna connecting my Linux box remotely with a graphic desktop environment, I have many choice, VNC (or VNC over SSH, VNC over VPN), SSH with X-window enabled, xdmcp, etc. Here we will discuss how to connect to your Linux desktop via “ssh -X”. It’s very easy, you just need to type two more letters than common SSH connection.

Why “ssh -X”? Because the graphic rendering job is done at your client so the data to transfer thru network is not huge. You won’t feel the screen is delayed even when you play movies. And this won’t add your server much load, as the same reason, thus a lot of job is done by your client. So, this is a high efficiency solution for remote desktop. You even can run big commercial graphic software, like Xilinx ISE or Mathworks MATLAB, remotely. And, this supports multi-client, no matter using different username or same username, since you a connecting to a server, both SSH server and X server.

Of course, you need to properly install and configure your SSH server, which is on the same machine running your Linux graphic desktop environment (KDE, GNOME, Xfce, or whatever). Obviously, you MUST install your SSH server program. You can install it via “sudo apt-get install openssh-server” on Ubuntu Linux 7.10. I think you can easily figure out how to do so on other Linux distributions. Then edit the file /etc/ssh/ssh_config. Make these lines be in that configuration file:

ForwardAgent yes
ForwardX11 yes
ForwardX11Trusted yes

Now open /etc/ssh/sshd_config. Attention, the file name is sshd_config, not the same as previous one. Make sure this line be in this configuration file

X11Forwarding yes

Restart your SSH server. Now, go to your client computer, from which you will connect to this computer.

I have no idea on how to do next on Windows. If your client computer runs on Linux or Mac OS X, or other OS with X server running, go ahead.

If your client computer runs on Mac OS X, make sure that you have installed X11 for Mac OS X. Go to “Application”- > “Utilities” to start X11 and you will see an xterm terminal in front of you by default. If no such window, click “Applications” – > “Terminal”.

Now let’s simply type

ssh -X user_name@the_server_IP_or_hostname.domainame

. For example, if my server is www.example.com and my username is NSF, I simply type

ssh -X NSF@www.example.com

. Accept the RAS key and enter your password.

Have logged in? Ok, the big show is coming. If your desktop is GNOME, then just type

gnome-session

. What do you see? The GNOME desktop is in front of you. If your desktop is others, such as KDE or Xfce, please refer their docs on how to start them.

Try to something, and you will really find that the networked remote desktop is very fast. You can even play movies. No delay, right? As I just said before, the graphic rendering job is done at your client so the data to transfer thru network is not huge. It’s just like when you play a 3D network game, like World of Warcraft, only some instructions are transferred thru the Internet but not all 3D objects.

This is my desktop connecting to remote Linux box from a Mac. The left-top corner lays Xlinx ISE. The left-bottom is playing 2008 New Years Concert. I put the Mac info page over the Linux desktop. Like it? DIY, now!