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Archive for the ‘System Administration’ Category

Choosing a VPS

Aug-21-2007 By miketeo

Some short notes on choosing a VPS

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Switching SELinux Modes

Aug-21-2007 By miketeo

SELinux has three operation modes:

  • Enforcement – this is probably what your box is in if you are having tons of problems with your services
  • Permissive – switch the SELinux kernel into a mode where every operation is allowed. Operations that would be denied are allowed and a message is logged identifying that it would be denied. The mechanism that defines labels for files which are being created/changed is still active.
  • Disabled – SELinux is completely switched off in the kernel. This allows all operations to be permitted, and also disables the process which decides what to label files & processes with.

Disabling SELinux could lead to problems if you want to re-enable it again later. When the system runs with file labelling disable it will create files with no label – which could cause problems if the system is booted into Enforcement mode. A full re-labelling of the file system will be necessary. Most of the time, setting your box to Permissive will resolve most of the problems.

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mailq displays a list of all messages that have not been delivered yet. The display contains: the queue ID; sending user; the size of the message and the time the message was created; the return address, and a list of the message’s recipients. If the message was already delivered or failed for some recipients, this will be indicated as well.

$> mailq

Checking Postfix Queue

Aug-21-2007 By miketeo

To check the various queues, use qshape. It prints Postfix queue domain and age distribution.

$> qshape incoming active deferred hold