Xen Bug: xen_net: Memory squeeze in netback driver (32bit PAE) // Crucial Paradigm

Basically what you are doing is ensuring that Dom0 will not be decreased in size, as when this happens it causes problems the the xen_net driver which can in turn cause network connectivity problems with your DomUs.

Tags: hypervm, server-administration, vds, xen

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Filed under: Uncategorized by — aaron @ 10:10 pm

June 5, 2008

How to upgrade Gentoo (emerge)

The basic way to upgrade Gentoo, is the following:

# emere –sync

Once this has been competed:

# emerge -uDv world

Tags: gentoo, linux, server-administration

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Filed under: Uncategorized by — aaron @ 10:06 pm

April 2, 2008

yum errror: error: install: %pre scriptlet failed (2), skipping …

Problem: If you are getting an error something like this when using yum:

Total download size: 549 k
Is this ok [y/N]: y
Downloading Packages:
Running Transaction Test
Finished Transaction Test
Transaction Test Succeeded
Running Transaction
error: install: %pre scriptlet failed (2), skipping screen-4.0.3-1.el5

Solution: Disable selinux

Tags: server-administration, xen, yum

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Filed under: Uncategorized by — aaron @ 6:02 am

April 1, 2008

Xen DomU: 4gb seg fixup, process

A common error on a Xen DomU (as well as Dom0) in /var/log/messages once the guest/VDS has just been setup is:

4gb seg fixup, process

You can fix this easily by doing the following on the guest/VDS:

mv /lib/tls /lib/tls.disabled
mv /usr/lib/tls /usr/lib/tls.disabled
echo ‘hwcap 0 nosegneg’ > /etc/ld.so.conf.d/libc6-xen.conf
reboot

Tags: hypervm, server-administration, xen

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Filed under: Uncategorized by — aaron @ 2:12 am

March 31, 2008

LVM: pvcreate /dev/sda4 gives error Device /dev/sda4 not found (or ignored by filtering).

If you are using the pvcreate command something like this:

pvcreate /dev/sda4

And it gives an error like this:

Device /dev/sda4 not found (or ignored by filtering).

This can sometimes be resolved by rebooting the server (if the LVM partition was just created, and the server has not yet been rebooted).

Tags: server-administration, servers

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Filed under: Uncategorized by — aaron @ 6:38 pm

March 19, 2008

HyperVM: VM creation has failed. Reason: Could not download __path_program_ or no_template_and_could_not_download []

HyperVM with Xen Error when trying to rebuild a VDS, or when trying to setup a new VDS:

VM creation has failed. Reason: Could not download __path_program_

no_template_and_could_not_download []

Solutions:

Ensure firewall is not running on slave, or incoming and outgoing port 8889 is allowed.

Set the permissions to 644 to the template (which is creating the error message) on the master server in the /home/hypervm/xen/template directory.

Ensure that the FQDN (fully qualified domain name) for the HyperVM master server (Servers -> localhost -> Information) is resolving to the correct IP.

Tags: hypervm, server-administration, vds, virtual dedicated servers, xen

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Filed under: Uncategorized by — aaron @ 10:12 pm

March 18, 2008

FreeBSD Installation Issues/Problems Error: BTX halted

When you receive the following error:

BTX loader 1.00 BTX version 1.01
Console: internal video/keyboard
BIOS CD is cd0
BIOS drive A: is disk0
BIOS drive C: is disk1
BIOS drive D: is disk2

BIOS 639kB/523264kB available memory

FreeBSD/i386 bootstrap loader, Revision 1.1
(root at wvu1.btc.adaptec.com, Mon Feb 23 18:35:51 GMT 2004)

int=0000000d err=00000000 efl=00030246 eip=00003034
eax=0000205d ebx=00000004 ecx=00002000 edx=0000288c
esi=00000904 edi=0006290c epb=00001538 esp=00001502
cs=f000 ds=ee00 es=ee00 fs=0000 gs=0000 ss=ee00
cs:eip=0f 20 dd 81 e5 00 f0 0f-20 c2 0f 01 e0 a8 01 75
08 80 e2 fe e8 53 ff eb-21 0f 20 e0 a9 30 00 75
ss:esp=0c 29 06 00 04 09 00 00-38 15 00 00 22 15 00 00
04 00 00 00 8c 28 00 00-04 00 00 00 5d 28 00 00
BTX halted

This error can occur when installing via a USB CD-ROM drive, or if you have a USB hard drive. The solution to this is to unplug them, and install without using that device.

Tags: freebsd, server-administration

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Filed under: Uncategorized by — aaron @ 1:56 am

March 16, 2008

Spamd child process causing high server load

Sometimes, spamd child process for a particular user can cause high server load. This is a bug with spamassassin and is reported here:

https://issues.apache.org/SpamAssassin/show_bug.cgi?id=5612

To fix the issue, apply the patch mentioned in the bug.

For cPanel servers, run the following scripts:

/scripts/autorepair spamd_dbm_fix
/etc/init.d/exim restart

Tags: cpanel, exim, server-administration, spam

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Filed under: Uncategorized by — aaron @ 2:59 pm

March 5, 2008

404 Error when to accessing /wp-admin/admin-ajax.php

When you receive this error:ForbiddenYou don’t have permission to access /wp-admin/admin-ajax.php on this server.

Additionally, a 404 Not Found error was encountered while trying to use an ErrorDocument to handle the request.

If you are receiving this error, then its likely you have mod_security installed on your server, and you will need to update your mod_security rules.

Find the following in your mod_security configuration:

Only accept request encodings we know how to handle
# we exclude GET requests from this because some(automated)
# clients supply "text/html" as Content-Type
SecFilterSelective REQUEST_METHOD "!^(GET|HEAD)$" chain
SecFilterSelective HTTP_Content-Type "!(^application/x-www-form-urlencoded$|^multipart/form-data;|^text/xml;)"

Change it to:

# Only accept request encodings we know how to handle
# we exclude GET requests from this because some (automated)
# clients supply “text/html” as Content-Type
SecFilterSelective REQUEST_METHOD “!^(GET|HEAD)$” chain
SecFilterSelective HTTP_Content-Type “!(^application/x-www-form-urlencoded;|^multipart/form-data;|^text/xml;)”

If you don’t have access to mod_security configuration (i.e. you are not the administrator of the server), then you can add the following to a .htaccess file for your site:

<IfModule mod_security.c>
SecFilterInheritance Off
</IfModule>

Tags: blog, cpanel, security, server-administration, wordpress

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Filed under: Uncategorized by — aaron @ 4:56 pm

March 5, 2008

Server hung at ‘Probing PCI hardware bus (00)’

Error: Probing PCI hardware bus (00), server hung at this message, while booting.

The problem can be fixed by adding the kernel flag ‘pci=nommconf’ in the kernel command line in the grub.

1) Reboot the server.

2) At the grub boot screen, select the kernel and press ‘e’ to edit the entry.

3) Select the kernel command line and press ‘e’ to edit the entry, which looks like

kernel /vmlinuz-x.x.x-x.x ro root=/dev/abc/ acpi=off

4) Add pci=nommconf at the end of the line, like

kernel /vmlinuz-x.x.x-x.x ro root=/dev/abc/ acpi=off pci=nommconf

5) Then press enter and press ‘b’ to boot.

Once the server reboots and comes online, edit the grub.conf and add ‘pci=nommconf’ in the default kernel’s kernel command line. (kernel /vmlinuz-x.x.x-x.x ro root=/dev/abc/ acpi=off pci=nommconf)

Tags: acpi, server-administration

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Filed under: Uncategorized by — aaron @ 2:53 pm