When you create someone a new Linux user account, it’s always a good practice to force them to change out the temporary password upon initial log in.
This effectively reset user creation date back to 01JAN1970, Unix time.
chage -d 0 $USER
Archive for January, 2010
Colors in “ls”
Jan 27
Many default Linux distributions came with ls pre-modified to display certain file/folder types in color. However, sometimes can be an annoyance on certain types of terminal screen.
Turn off coloring:
ls –color=none
or
unalias ls
Turn on coloring:
ls –color=auto
Busy busy busy…
Jan 26
Not much updates because of business…
Things are pilling and not going away… that’s the way of life! 
GNU screen – multiuser
Jan 22
(For the sake of this post, let’s use root and ignore the setuid bit. )
GNU Screen is like the next best thing since slice bread. A MUST for any systems administrator. I would not have it without screen for my day-to-day life. Yup, that’s how useful it is!
Screen do support multiuser, single session mode. Meaning you can have multiple users connect to same terminal session and share the interaction that way. Pretty useful when you try to teach someone something. Think web conferencing at CLI level.
Once you started your screen session, you can run following to turn on multiuser mode (default is off).
*press hold “CTRL” and press “a” at same time* (Ctrl-a)
Type “:multiuser on” (make sure you start with the colon!)
Now someone else can attach to the same session with following. Saying if you started your screen session with name “test”.
screen -x test
#chkconfig: 2345 80 05
On a Red Hat variant server, all init files in /etc/init.d/ have the above commented line. 2345 denotes to start the particular script in runlevels 2,3,4,5. 80 denotes start-up priority and 05 denotes the stop priority.
VPS providers review
Jan 21
VPS (Virtual Private Server) is very much like a dedicated server, but at a lower scale. Meaning you may be resource bound – maximum CPU speed capped and applied I/O threshold. UnixTitan.net is running under a VPS.
This post is meant to be updated from time to time. Noting my experiences with various VPS host providers. Several things to keep in mind, in order of importances to me: 1) stability 2) network speed 3) VPS speed 4) customer support 5) price. I think regardless what type of hosting you have, you will want your service to be up-and-online available to everyone. Your in-the-end goal might be different than mine, but I do not care if the VPS company is new or not. I just want my service to be online 99% of the time.
I actually started this post because CpanelHost.me enraged me! This is the second time I tried this host. First time I rented for a month (Nov 2009), and that month I had zero issues. However, second time around I wasn’t so lucky.
I am using CpanelHost.me VPS to provide a secondary passive HA server for a client. Guess what, it’s been down for about almost 40 hours. No response to my support ticket neither.
From the response I got from last ticket, it seems some kid(s) is running CpanelHost.me. See below. I merely asked why my VPS IP lookup ends up in Russian Federation and that’s the response I got.
russian federation???loll no the server is in usa, PA.
Seems like they are a BurstNet reseller. I got their 512MB/768MB plan. Everything else has been pretty decent. I do not recommend CpanelHost.me unless you got $5 to loss.
Review date: 22JAN2010
Stability: 9/10
Network speed: 8/10
VPS speed: 8/10
Customer support: 3/10
Price: 10/10
This is actually one of the best VPS companies I’ve used. However, due to some technical issues I had to leave them. They even went out of their ways to refund me the full two months.
They use Xen. It seems all their VPS is HVM-ed. Why? They used to be a VMware shop. I was told it’s easier for them to convert and track things by uniforming all VPS in HVM mode. No problems with me. It’s only few extra percent of overhead added on top between paravirtualized & HVM mode.
This is actually the second time I’ve used them. I used them earlier last year when they were still on VMware.
I’ve submitted like close to ten support tickets. All has been answered less than ten minutes. Now this is what I call customer support!
The reason I left them is because we discovered Debian was getting less than subpar I/O performance than their counterpart CentOS guests. It was in the 20MB~40MB range compared to the typical 200MB+ I/O. Their tech tries to make an exception for me by converting my VPS to be paravirtualized. However that was shot down. Because the intention for the VPS is to be gradually pick up more and more usage over time, I don’t want to take the chance maxing out I/O few months down the road. I made the tough decision of leaving them.
(I also have some lock-up issues initially, but that was resolved by adding more vCPUs.)
I strongly recommend Database by Design, LLC VPS!
Review date: 22JAN2010
Stability: 9/10
Network speed: 9/10
VPS speed: 7/10
Customer support: 10/10
Price: 8/10
Solaris disable/enable GUI
Jan 20
I personally do not care for GUI on *nix, I MEANT on servers of course. Below shows how to disable/enable GUI in Solaris.
- Disable GUI
/usr/dt/bin/dtconfig -d
- Enable GUI
/usr/dt/bin/dtconfig -e
Following easily sorts top 10 programs using the most CPU time or memory.
- Sort by CPU
prstat -s cpu -n 10
- Sort by memory
prstat -s size -n 10
Create more SWAP in Solaris
Jan 20
To continue over from my previous tip – Create more SWAP in Linux. Here is how to do the same thing in Solaris!
Let’s create desired file first. Say we want to add 512M additional to existing swap.
/usr/sbin/mkfile 512m /swapfile.512MB
Tell Solaris to activate /swapfile.512MB swap file.
/usr/sbin/swap -a /swapfile.512MB
You can verify total amount of swap in use with following.
top -d 1 |grep “swap in use”
Run “top” just once!
Jan 20
Ever need to run top just once? Perhaps you need it to pipe into a parser or another program.
- Linux
top -bn 1
- Solaris
top -d 1