This article requires more details with links to the other upgrade options. Maybe even have a general intro page on updates. Also, the same steps to record the Ubuntu version information before running the update.
In a server environment there are different levels of updates,
- upgrade - Package Update without removing packages
- dist-upgrade - Package Update using conflict resolution to remove outdated packages
- do-release-update - Release Updates
This is to allow the administer fine grained control. The more higher level of updates, the more risk to a system.
Package Update using upgrade is the safest and covered in Setup Ubuntu Linux Base Server. The command to upgrade is,
A reboot is almost never required, but you can verify that the reboot file does NOT exist,
From the man pages,
Once the system actually is in production you will want to review what will be upgraded before actually performing the upgrade. This can be performed using --simulate,
You may notice with apt-get upgrade that even though there are some updates not yet installed, they get "kept back". That is because these are considered more intrusive updates and will only be installed through a dist-upgrade.
This type of upgrade often updates the the Linux kernel in which case reboot is required to change to the new kernel.
From the man pages,
There are some additional considerations when performing a dist-upgrade when a kernel upgrade is on the list,
- Have console access - in some rare cases, on boot-up you will want to choose to go back to your previous kernel.
- Be prepared to reboot - for the kernel to take effect you will need to reboot your machine.
Check to see if kernel upgrade is available,
Notice line 5 indicates that kernel upgrade is required because of the keyword image.
Record the current kernel information. In this example, the current kernel version is 2.6.32-33,
Run the upgrade,
Pay attention to the kernel information. For example,
In the above response, we can see that the new kernel version will be 2.6.32-40.
Check for Reboot
First, check if a program requires a reboot by looking for the reboot-required file. If the file does not exist you will not need to reboot.
However, that's not the end of it. Sometimes this file will not populate even though it should. For example, if you run the kernel version commands you might find, as in the below example, the updated kernel has not yet taken effect. In this case, a reboot would be required to use the updated kernel.
If all goes well you will get back in. If not, get console access, reboot the system and select the previous kernel during the initial boot.
Optionally, verify the new kernel is running. For example,