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Mac OS X - keyboard shortcuts on startup

If you want to use functions described below just hold down key or keys' combination when your computer is starting.

If key(s) function don't work it can mean that you don't have genuine Apple's keyboard

Start in verbose mode
 

COMMAND
+
V

 


 

COMMAND
+
S

 


Boot from CD or DVD
C

 


Display start manager (all bootable devices/systems)
 

OPTION

 


Start in (safe mode)
 

SHIFT

 


How to resolve "Cannot mount ext4 filesystem" problem?

After last kernel update I have run into problems with starting system. My computer cannot start the system with new compiled kernel version. Only thing that I changed was root partition type. I've changed it from ext3 to ext4 filesystem. When I tried to run system with new kernel I receive this message:

mount: cannot remount block device /dev/sda2 read-write, is write-protected
 

Resolution

dmesg gives the answer, it says:

EXT4-fs (sda2): Filesystem with huge files cannot be mounted RDWR without CONFIG_LBDAF 

You need to compile your kernel with "Support for large (2TB+) block devices and files" enabled (CONFIG_LBDAF option in kernel config).


Release of Cyrus IMAPd 2.4.9beta2

There is new Cyrus IMAPd 2.4.9beta2 version available to download.You can download it from the snapshots directory: This is an beta release in the 2.4.x series. It fixes couple of bugs in the "deliver" and lmtp codepaths and adds a couple of wishlist items. It also reverts the LMTP delivery fix for Bug #3163, which was implicated in Sieve issues at FastMail.

WARNING! One known bug that still exists is that quota -f can cause ALL quotaroots to believe they have twice their actual usage. This bug is still present in 2.4.9beta2 as well as beta1. This problem has always existed, but is much worse because of a bug in 2.4.8 where user renames caused quotaroots to become incorrect. The recommended workaround at this time is to run quota -f TWICE any time you need to run it. The first run should fix any incorrect quota roots, and the second run will fix all the doubled quotas caused by the first one.

3 commonly used ways to find Ubuntu version that you have

Have you ever forgotten which Ubuntu version you are using? If it's true here you will find methods how to check Ubuntu version that you are curently running.

Simplest ways to find Ubunt version:
 

1. Use lsb_release command

Simply run from command line:
  lsb_release -a

2. Find Ubuntu version inside /etc/issue file

Simply edit or cat issue file like below:
  cat /etc/issue

3. Check ubuntu version in lsb-release file

  cat /etc/lsb-release
Those are most commonly used ways to check Ubuntu version which your system is running from the command line level.

Mac memory test.How to test your Mac OS X RAM?

Has your Mac OS X system crashed many times? Have you had problems with running applications? If your answer is 'yes' - probably you have some troubles with your Mac RAM memory sticks. There are some methods to test memory modules. You should do Mac memory check! I will show you how to do your Mac memory test.

What to do after ORA-01658: unable to create INITIAL extent for segment in tablespace string?

Lately I've been getting into some troubles with free space in one of Oracle's table. The reason is that I didn't use option AUTOEXTEND when I created the table. If you use AUTOEXTEND option when a table is created, Oracle will extend the table when needed, but sometimes when you need to have more control on space usage don't use AUTOEXTEND option. The only way to get rid of that error is:

1. Clean up table - remove unneeded data

2. Manualy extend database

    ALTER DATABASE DATAFILE 'full_path_to_file' RESIZE 500M;

SPFile, PFile - What is used by your running Oracle's instance?

From time to time I need to check what initialization parameters my Oracle's instances are using (init.ora or spfile). You changed your instance's parameters but after restart you can see the old ones? Have you had a similar problem? Have you got enough of it? The solution is simple.

Open sql console and enter sql command like below:
 
    sqlplus / as sysdba
    SELECT DECODE (value, NULL,'PFILE', 'SPFILE') "Init File Type" FROM v$parameter WHERE name = 'spfile';

Init F
------
PFILE
In my case init.ora (PFile) is used. You can do it also another way. I will show you second possible way to check that. Now I will ask for Oracle parameters called 'spfile' and 'pfile' (similar to previous example) In sqlplus console enter:
  SHOW PARAMETERS 'spfile';

NAME                                 TYPE        VALUE
------------------------------------ ----------- ------------------------------
spfile                               string

The rule is simple - if 'spfile' parameter have NULL value it means that Oracle uses PFile (init.ora file) - in another case Oracle uses SPFile.

What to do after ORA-12162?

After installing Oracle XE on Debian I got into problems with connection to Oracle's instance. Every connection ended with error 'ORA-12162 TNS:net service name is incorrectly specified' Resolution is very simple - you only have to set correct environment variables:

    export ORACLE_SID=XE
    export ORACLE_HOME=/usr/lib/oracle/xe/app/oracle/product/10.2.0/server
 

and that's all After that you should also make this change permanent by writing those settings to shell initialization file. For Debian it will be /etc/profile (globally) or per user (.bashrc in user directory) I'm really missing /etc/env.d directory from Gentoo distro...