Robots Kill People...

Enable Ubuntu 8.10 Root Password

Jason — Wed, 14 Jan 2009 19:44:28 +0000

One of my main frustrations with Ubuntu has always been the lack of a usable root account.

As a result, I've taken to enabling the account on all of my boxes.

All you have to do is assign a password to the account:

Code:

sudo passwd root

and if you decide to disable the account later:

Code:

sudo passwd -l root

If you do add a password to root, don't mess with the sudoers file, as if you disable root in the sudoers file and later disable the account itself, you won't be able to do anything and will have to use a livecd to fix it.

Original post blogged on b2evolution.

ORA-27121: unable to determine size of shared memory segment

Jason — Wed, 14 Jan 2009 16:41:13 +0000

Installing Oracle 10G on Ubuntu this morning...

Got the following error:

Code:

ERROR:
 
ORA-01034: ORACLE not available
 
ORA-27121: unable to determine size of shared memory segment
 
Linux Error: 13: Permission denied

This is caused by Oracle installer not setting setuid on $ORACLE_HOME/bin/oracle. To fix do:

Code:

$ cd $ORACLE_HOME/bin
$ chmod 6751 oracle

Original post blogged on b2evolution.

Flush DNS Cache on OSX Leopard

Jason — Wed, 14 Jan 2009 14:17:39 +0000

The method for flushing the DNS cache on OSX has changed with Leopard.

Here is the right way:

Code:

dscacheutil -flushcache

the old method (lookupd) has been deprecated.

Original post blogged on b2evolution.

Add Swap to Linux...

Jason — Tue, 13 Jan 2009 18:30:06 +0000

This is an old sysadmin trick, but a good one all the same.
Suppose that you finished installing a brand-new Debian GNU/Linux server, and for whatever reason you forgot to set aside some space for a swap partition. Or you correctly got some swap space at installation time but now you desperately need some more. Well, despair not. It’s a little known fact that you can have swap space in a file on top of the filesystem instead of using a dedicated block device.
This simple recipe will give you 2Gb of swap space. Here we go:

Code:

# mkdir /var/swap
# chown root.root /var/swap
# chmod 700 /var/swap
# dd if=/dev/zero of=/var/swap/01.swp bs=1024 count=2M
# chown root.root /var/swap/01.swp
# chmod 600 /var/swap
# mkswap /var/swap/01.swp

Now add this newly created swap space to your /etc/fstab:

Code:

/var/swap/01.swp none swap sw 0 0

Theoretically, you won’t get the same performance as using a dedicated block device, and if the file actually gets fragmented it might drop rigt to the floor, so if you try this at all do it as soon as possible after installation. So if what you’re trying to do is to *increase* your available swap space instead, you may add a priority option to give preference to the block-device swap space:

Code:

/dev/hda1 none swap sw,pri=1 0 0
/var/swap/01.swp none swap sw,pri=2 0 0

And just this time activate the swapspace with addswap (The initscripts will do it on every boot thereafter):

Code:

# swapon -av

That’s all there is to it.

Original post blogged on b2evolution.

IE7 and PHP $_SESSION Vars...

Jason — Sat, 10 Jan 2009 22:24:19 +0000

OK, most people have heard of the dreaded IE7/PHP $_SESSION[''] nightmares... and there are about a million different solutions out there.

Here is the bit of code that worked for me:

Code:

<?
header('P3P: CP="CAO PSA OUR"'); 
session_start();
...
...
?>

It turns out that you have to add a special header before opening the session.

Original post blogged on b2evolution.

	`ERROR:`

	`ORA-01034: ORACLE not available`

	`ORA-27121: unable to determine size of shared memory segment`

	`Linux Error: 13: Permission denied`

	`# mkdir /var/swap`
	`# chown root.root /var/swap`
	`# chmod 700 /var/swap`
	`# dd if=/dev/zero of=/var/swap/01.swp bs=1024 count=2M`
	`# chown root.root /var/swap/01.swp`
	`# chmod 600 /var/swap`
	`# mkswap /var/swap/01.swp`

	`<?`
	`header('P3P: CP="CAO PSA OUR"');`
	`session_start();`
	`...`
	`...`
	`?>`

	`/dev/hda1 none swap sw,pri=1 0 0`
	`/var/swap/01.swp none swap sw,pri=2 0 0`

	`$ cd $ORACLE_HOME/bin`
	`$ chmod 6751 oracle`