CentOS Update

Keeping your packages up to date is important to prevent running into known and already fixed bugs as well as patching any security vulnerabilities that might have been found by the distribution and package maintainers. Its not hard to do so lets get right to it.

The first command you want to know is yum check-update. If you are not familiar with yum, read our primer on yum first and then come back here. The check-update command will print out a list of any packages for which an update is available. For scripting purposes it will also return an exit value of 100 if updates are required, 0 if no updates are required or 1 if an error occurred.

Here is an example of how to check for updates in CentOS:

yum check-update > /dev/null
RC=$?
if [ $RC -eq 100 ]; then
   echo "Updates are needed"
elif [ $RC -eq 0 ]; then
   echo "No updates are needed"
else
   echo "An error occurred in the package update check, try again"
fi

yum check update centos

And here is an example of printing out the updates as needed:

yum check-update > ./output
RC=$?
if [ $RC -eq 100 ]; then
    cat ./output
fi

We can also check updates for a single package with yum update and NOT specifying Y, for yes, when asked. If you do press Y, for yes, the update will proceed for the specified package. For example I will do a check on the package vim-minimal now:

yum update vim-minimal

If you want to proceed and update all packages, then go ahead and run yum update and do not provide any package names. It will find all out of date packages and update them all after you confirm Y for yes at the prompt.

# yum update

yum update

After the update is complete you can re-run the check script above and expect to see nothing to update.

yum check-update > /dev/null
RC=$?
if [ $RC -eq 100 ]; then
   echo "Updates are needed"
elif [ $RC -eq 0 ]; then
   echo "No updates are needed"
else
   echo "An error occurred in the package update check, try again"
fi

CentOS no update needed

Conclusion

Its important to keep your CentOS system up to date. You can use the above methodology to help.

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