Andryan’s Random Notes

In case you wonder why “Add Photos” link on your Facebook Page is no longer working as expected (directs you back to your Facebook Home), I believe it’s because they have changed the way fan photos work on Facebook Pages (without informing users).

Like usual, Facebook developers are changing and implementing things quickly without updating all necessary help information to guide users with these changes.  These days bugs are easily spotted on Facebook.  It’s understandable to have bugs at their current size, but implementing changes before/without communicating these changes to users is a very stupid move.  Not to mention they never reply to (real) bug reports.

Two weeks ago, for 1 day, no one could write a comment to wall posts of the Facebook Pages.  Only comments for photos were normal.  I think I’m starting to hate Facebook, plus the fact that they have removed Profile’s boxes and tabs.  Someone should really make a good copy of Facebook when it had all the cool features.

These past 3 days I have waited for a reply from Facebook to fix or at least address fan’s “Add Photos” link issue, but I got nothing.  I need this feature to work ASAP for my marketing team, so I looked around and found a discussion link on Facebook.  Basically these people complain about the same thing, apparently this feature has been buggy since last year.

Abbey Butler‘s post on page 7 of the thread is the answer.  Thanks, Abbey!

First of all, avoid any green drives (including WDC RE-GP drives) at all cost for RAID setups.

I have Areca’s ARC-1210 and ARC-1220 RAID cards installed on my Tyan servers (with S5397 and S5211 motherboards).  Some of these servers are using WDC GP drives (my vendor ordered the GP drives), despite having TLER-enabled, they will drop from the RAID sets within days or weeks.  Enabling TLER does help, but don’t count too much on it.  This is caused by the IntelliPower feature that limits its RPM to 5400.  RAID drives are supposed to be fast, GP drives are slow.

Few weeks ago I tried to get a pair of WDC WD2500AAJS-22VTA0 to run Windows Server 2003 R2 Standard Edition.  The installation went well until few days of uptime, the server rebooted itself after showing this error message:

The instruction at “0×76946203″ referenced memory at “0×76946203″. The required data was not placed into memory because of an I/O error status of “0xc000000e”. Click on OK to terminate the program.

Prior to this error message, it showed a yellow popup (like the low disk space popup) on the systray but I couldn’t get a screenshot as it happened really fast.  It states (IIRC) that files are missing/corrupted in the RECYCLER folder.

I tried disabling write cache on the RAID card and Windows, but no luck.  Tried to enable TLER (it wasn’t on before), also no luck.  Finally I consulted Google and found out that disabling NCQ help on some hard drives.  I disabled NCQ and rebooted the server, so far it has been up for almost a month.  Before this, it couldn’t even reach a week of uptime.

Now I use the WDC RE3 drives (WD5002ABYS) to replace the GP drives.  The temperature of the RE3 drives are much lower (8-10C lower) than the desktop drives, despite having less cooling in the room.

Hopefully this post can help others to avoid the issues I encountered.

If you wonder why your VPS or specifically OpenVZ VE’s ntpd is stuck at stratum 16 or stratum 0 while ntpq -p shows no abnormality (use ntpq -c rv to check state, it should say state=3 when abnormal), then try executing ntpdate manually. If it says “ntpdate: step-systime: Operation not permitted”, then you need to reconfigure your OpenVZ VE or ask your host to do it for you: vzctl set 123 –capability sys_time:on –save

If everything is fine but this message “ntpdate: no server suitable for synchronization found” keeps coming up, then it could be your ISP blocking UDP port 123. Use ntpdate -u to verify, this option should circumvent the firewall.

References:
http://blog.haite.ch/2009/05/22/1242984900000.html

PREROUTING in nat table: DNAT, REDIRECT
POSTROUTING in nat table: SNAT/MASQUERADE

PREROUTING in mangle table: alter routing (e.g. source-based routing)
FORWARD in mangle table: traffic shaping for tc (flowid)

In MikroTik RouterOS, /ip firewall nat:
srcnat chain = PREROUTING
dstnat chain = POSTROUTING

/ip firewall mangle:
prerouting chain = global-in
forward chain = global-out (support NAT traffic shaping, higher load on router)

Update: I used to think that global-in literally means global input, while global-out literally means global output.  Apparently I was mistaken.  The parent queues MUST be matched to the right parent, either global-in, global-out, global-total, or one of the network interfaces depending on the mangle rules.  Top-most queue parent (global-in, global-out, global-total) doesn’t decide whether it’s up/down.  The mangle rules do the direction decision trick, whether a packet is incoming/download or outgoing/upload.  This makes perfect sense now! (doh)  I kept wondering why half of my queues (download queues’ top-most parent was global-in) weren’t working, when all my mangle rules were in forward chain.  Obviously they wouldn’t, because global-in marks both direction in prerouting chain.

Update 2: mangle: download rules first then upload rules. global-in, connection mark: prerouting; packet mark: prerouting. global-out, connection mark: forward, packet mark: postrouting.

This didn’t make sense until I read the URL listed below under References.  Silly me!  Assumption is the root of most, if not all, problems indeed.

References:
http://wiki.ispadmin.eu/index.php/Documentation/Mikrotik_guide#.22Global-in.22_vs._.22global-out.22_setup

I have a MikroTik router (RouterOS v4.x) with an ADSL connection at work, unfortunately it comes with dynamic public IP address.  I need to connect to my office workstation or simply the MikroTik router from home or elsewhere but I need to know its latest IP address all the time, so I decided to use ZoneEdit’s Dynamic DNS service.

Add a new script to the MikroTik router (replace those in bold):

• /system script add name=zoneedit-dyndns source=”/tool fetch url=\”http://dynamic.zoneedit.com/auth/dynamic.html\?host=dyndns.example.com&dnsto=127.0.0.1\” user=ZEUser password=ZEPass keep-result=no\r\n/delay 30\r\n/tool fetch url=\”http://dynamic.zoneedit.com/auth/dynamic.html\?host=dyndns.example.com\” user=ZEUser password=ZEPass keep-result=no” policy=read

Test the script by running it manually:

• /system script run zoneedit-dyndns

If it shows 2 lines of “status: finished”, then the script works properly.

Schedule the script to run regularly (in this case, every 10 minutes):

• /system scheduler add name=”zoneedit-dyndns” interval=10m on-event=”/system script run zoneedit-dyndns” policy=read,test

Why does it require 2 “fetch” commands to update?  I think there is a bug in ZoneEdit’s Dynamic DNS updater, so it needs to be forced. The new dynamic DNS change entry has to be significantly different from the previous dynamic DNS entry before the ZoneEdit backend would really update it.

Thanks, ZoneEdit!

If you need an SSH client for BlackBerry, you can use MidpSSH. However, this client doesn’t allow you to use your BIS subscription. Luckily someone has modified MidpSSH to work over BIS.

Once you have installed the modified MidpSSH, there is a very good chance that your mobile operator blocks outgoing TCP port 22 on your BIS plan. You need to reconfigure your SSH server to listen on another port (port 2222 works for me).

In case you wonder how to specify the custom port (since there is no specific port field), specify the port in the Host field, e.g. 127.0.0.1:2222.

Hope this helps!

I just purchased a VPS account from a local VPS provider (using HyperVM). The first thing I was to rebuild the VPS because it has LXAdmin installed by default. I want a lightweight VPS with everything minimal.

I was excited to see some minimal OS templates on the web Control Panel. I have a Debian 4.0 UK VPS. This time I choose Ubuntu 6.06, because there are lots of Ubuntu repository mirrors in Indonesia.

Once I rebuilt the VPS with Ubuntu template, the VPS cannot be instantly ssh’d into. sshd fails to start because  udev is installed and we need to remove that. Quickly remove udev by typing the following on Command Center: apt-get -y remove udev

Once it’s removed, reboot the VPS. Voila! You should be able to login using SSH now.

No need to do mknod /dev/random c 1 8, mknod /dev/urandom c 1 9, /sbin/MAKEDEV tty, /sbin/MAKEDEV ttyp, nor /sbin/MAKEDEV pts.

References:
http://prajizworld.com/?p=5

I have several Tyan TA26 B5397 barebones (with latest BIOS) which need to be installed with FreeBSD 6.3-RELEASE (32-bit). The installation went smoothly, but after finishing post-install setups and exiting the setup program, it wouldn’t reboot.

Initially I thought this was a small issue but eventually after the system boots up, I couldn’t restart the system with reboot, shutdown, nor init 6. It would stuck/freeze/hang at the “Uptime: …” line and before the “Rebooting..” line. I tried with 2 other barebones thinking that it is hardware issue, I got same results though. Clearly this is a bug in FreeBSD 6.3-RELEASE’s kernel.

I tried installing FreeBSD 6.4-RELEASE (32-bit) and it restarted properly. I was going to update the system to 6.3-STABLE — the server has to run 6.3, as 6.4 is not acceptable yet due to software compatibility issues — to see if the issue has been addressed in the -STABLE branch, but when I tried recompiling the kernel with PAE (in addition to SMP) support (still using -RELEASE kernel source tree), the reboot problem disappeared. YAY! I got it the fix by accident!

I’m not sure what is wrong since similar reboot problem seems to be popping around randomly since FreeBSD 5.X (after doing some Google searches). Browsing the PR database of FreeBSD didn’t help much either. Maybe if you know exactly what is wrong, you can share it here to help others with similar problem.

If you see an error like the following when compiling, then most likely it’s the errno.h problem:

/usr/bin/ld: errno: TLS definition in /lib64/libc.so.6 section .tbss mismatches non-TLS reference in envdir.o
/lib64/libc.so.6: could not read symbols: Bad value
collect2: ld returned 1 exit status
make: *** [envdir] Error 1

If there is a conf-cc file, then add “–include /path/to/errno.h” to the gcc line. Normally the file is at /usr/include/errno.h.

References:
http://cr.yp.to/docs/unixport.html#errno

References:
http://www.widianto.org/2006/08/18/source-based-routing/