Split Horizon

chmod’s man page doesn’t apparently explain it but “t” and “T” are both signifying a sticky bit, the difference is whether executable flag is set for other or not:

drwxrwxr-T     1774
drwxrwxr-t     1775

What follows is a copy-paste of this Skype forum post. I’ve tested this on 10.8.2. Seems to work.


We do not officially support or recommend running two instances of Skype simultaneously on the one computer. However, it is possible to do this:

Make a copy of Skype:

  1. Open Finder.
  2. In the sidebar, click Macintosh HD > Applications.
  3. Click Skype to select it.
  4. Press Cmd+C, then Cmd+V to copy and paste Skype.
  5. Skype copy appears.

Change the bundle identifier in the Info.plist file:

  1. Right-click the copy of Skype and select Show Package Contents.
  2. Click the folder named Contents, then open the Info.plist file.
  3. In the Info.plist file, locate the bundle identifier setting, com.skype.skype and change it to com.yourname.skype (for example: com.john.skype).
  4. Go to File > Save, and then close the file.

Change the data path used by Skype for storing data files:

  1. Open Terminal (Go to Finder and in the Search field, enter Terminal).
  2. In the Terminal window, enter the command:
    defaults write <new bundle identifier > DataPath <”path to a new data directory”>
    For example:
    defaults write com.john.skype DataPath “~/Library/Application\ Support/Skype\ copy”

Note: after Microsoft had terminated support for older versions and forced everyone to update their Skype this step returns an error now:

2014-08-23 11:13:58.912 defaults[45773:707]
Rep argument is not a dictionary
Defaults have not been changed.

However, I just ignored it and started up Skype and it worked. I can still run two copies of Skype as before.

  1. Press Return.


You can rename Skype copy to anything you’d like it to be. For example, you could use Skype business instead. This comes in handy, because when placed on a dock a tooltip will display this Skype business name and make easy for you to distinguish which Skype dock icon represents what instance.

In my setup I run Arch Linux and NFSv4 server on this system. I’d like to connect to any of the shares thatare available on this laptop server and write to them from the Finder in Mac OS X.

NFS Configuration

First things first, the Arch Wiki:



Then you get NFS and its dependencies installed.

Now, NFS configuration.

I export just one folder, /srv/nfs4/seagate1TB. NFS4 has the concept of the root for the exports and that’s what /srv/nfs4/ is exactly. Access is granted exclusively to specific /29 network.


/srv/nfs4/ xxx.xxx.xxx.0/29(rw,fsid=0,no_subtree_check)
/srv/nfs4/seagate1TB xxx.xxx.xxx.0/29(rw,insecure,no_subtree_check,nohide,all_squash,anonuid=1000,anongid=1000)

I encourage to read ‘man exports’, specifically General Options, User ID Mapping and EXAMPLE sections.

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The setup consists of Mac OS X system that runs RealVNC client to connect to Ubuntu Server machine that is a KVM host via VNC.

When working in guest VM graphical console (as opposed to text console which usually requires additional configuration of guest VM; see screenshot below) you must click into the black area and that grabs mouse pointer. Actually, you don’t have to click VM screen area if all you want to do is type on your keyboard but if you must use mouse it’s going to get locked. To release it normally a user has to press Ctrl_L+Alt_L as it is stated in the window title.

Screen Shot 2013-01-31 at 5.18.48 PM

However, it doesn’t work for whatever reason!

Quite accidentally I’ve established that pressing


has the same effect.

And so it works! :P

GnuCash can deal with multiple currencies. However, its behavior when setting currency exchange rates is somewhat obscure and had me spend literally hours to figure out how to get it under control a couple of times.

The use case. Account A is in USD currency, account B is in UAH currency. You need to transfer funds from A to B, which involves currency exchange rate.

When you do this the very first time, you enter Description of the transaction, specify the account B to transfer funds to, and key in Debit/Withdraw value of say 150USD and then hit Enter key, GnuCash then will present you with an exchange rate editor window where you should be able to enter the exchange rate for this transaction.

As it often happens, many transactions are repetitive, and luckily GnuCash helps making these records fast by offering you a history autocompletion function, much like one found in LibreOffice and Bash/Linux/UNIX terminal.

So, typically a user would quickly create another new record in a ledger for account A, specify a different amount of Debit/Withdrawal this time and find out that the resulting value in account B is wrong.

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What I mean by the title of this post is that sometimes ubuntu folks push security updates to $release-updates repository (I’m told this is so that they propagate faster across all the mirrors). So, when that happens, to APT they look as coming from $release-updates repository ONLY.

Which means unattended-upgrade is fooled into thinking there are no security updates available and so it never installs them automatically despite all the configuration instructing it to do so.

Good thing my little software updates report script can show these security updates regardless, that’s how I know about this.

The trick is as simple as having a separate list file for security repositories and then use only this file with apt via -o flag.

sudo sh -c 'grep ^deb /etc/apt/sources.list |grep securi >> /etc/apt/sources.security.repos.only.list'

apt-get -s dist-upgrade -o Dir::Etc::SourceList=/etc/apt/sources.security.repos.only.list

This is just an observation I made a couple of days ago. I had my new Macbook Air 11″ on for some 13hrs during which all I did was light use of Google Chrome to look up things once in a while, chat with people in Skype and Adium, listen to radio streams in iTunes, work in a terminal, of course, had Mail.app running which is configured not to save anything to disk, and by the end of the day Activity Monitor reported some 5GB worth of disk writes. 5 gigs, really?

Why would I be concerned? Well, I’m generally speaking curious, but also there’s a legitimate concern because SSD drives, which are of MLC type in Macbook Air’s, on average are guaranteed to last 5 years with average 40GB disk writes per day. So, you can see that 5GBs per day in that context isn’t really small.

So, I set out to figure out to see distribution of those disk writes but I haven’t found a solution yet. dtrace looks like the tool that could pull out this data but it falls short of showing accumulated values over time. What I’m talking about is Linux equivalent of iotop -o -a, which is just amazing, simple and user friendly compared to dtrace.

Which reminds me to say that Mac OS X is a funny OS. It makes it really easy to use a computer in GUI department, but Apple seems to have applied their philosophy of simplifying things to command line applications as well. Less of (otherwise useful and detailed) output seems to be characteristic of Apple’s version such tools as iotop and sar to name a few.

This I find a little frustrating and limiting. By and large, though, I really like Mac OS X and the whole experience of running Macbook Air.

I’d highly recommend it.



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