yum Invalid System Credential error

I ran across the following yum error after migrating a system from being a client of Satellite 5.6 to Satellite 6.1.  First here is the error:

# yum update
Loaded plugins: package_upload, priorities, rhnplugin, search-disabled-repos, security, subscription-manager
There was an error communicating with RHN.
RHN Satellite or RHN Classic support will be disabled.

Error Message:
    Please run rhn_register as root on this client
Error Class Code: 9
Error Class Info: Invalid System Credentials.
     An error has occurred while processing your request. If this problem
     persists please enter a bug report at
     If you choose to submit the bug report, please be sure to include
     details of what you were trying to do when this error occurred and
     details on how to reproduce this problem.

Setting up Update Process
rhel-6-server-rpms                                                                                                                                                            | 2.0 kB     00:00     
rhel-6-server-satellite-tools-6.1-rpms                                                                                                                                        | 2.1 kB     00:00     
No Packages marked for Update
This left me scratching my head for a few and a quick search didn’t produce much so I thought I should document this for prosperity.
The problem was with the contents of the file /etc/yum/pluginconf.d/rhnplugin.conf
Part of my transition is running this command:
sed -i -e 's/enabled=1/enabled=0/g' /etc/yum/pluginconf.d/rhnplugin.conf
The problem was unlike all of my other systems, this file must have been edited because instead of containing “enabled=1” it contained “enabled = 1”
To correct that I modified my sed command to ignore white space:
sed -i -e 's/enabled\s*=\s*1/enabled=0/g' /etc/yum/pluginconf.d/rhnplugin.conf

More details can be found using the yum.conf man page.

Hope that is helpful.


Working with Repositories

Pulling packages from multiple sources can lead to problems.  If you are running rhel and have epel enabled an update could inadvertently pull down a newer version from the wrong repository.  This doesn’t always cause a problem, but it can.  If you need to tfind all the epel packages on your system, here is how you: List all packages installed from repo “X”

yum list installed | grep @epel



Rhel6, Rhel7 Comparison

Moving from Redhat 6 to Redhat 7.  There are a *lot* of differences to get use to.  It is like having a friend come over and rearrange your entire house, including all the closets and cupboards!! You know it is your house, you just can’t seem to find any of your stuff!

Features RHEL 7 RHEL 6
Default File System XFS EXT4
Kernel Version 3.10.x-x kernel 2.6.x-x Kernel
Kernel Code Name Maipo Santiago
General Availability Date of First Major Release 2014-06-09 (Kernel Version 3.10.0-123) 2010-11-09 (Kernel Version 2.6.32-71)
First Process systemd (process ID 1) init (process ID 1)
Runlevel runlevels are called as “targets” as shown -> -> -> -> -> -> ->

/etc/systemd/system/ (this by default is linked to the multi-user target)

Traditional runlevels defined :runlevel 0

runlevel 1

runlevel 2

runlevel 3

runlevel 4

runlevel 5

runlevel 6

and the default runlevel would be defined in /etc/inittab file.


Host Name Change with the move to systemd, the hostname variable is defined in /etc/hostname. In Red Hat Enterprise Linux 6, the hostname variable was defined in the /etc/sysconfig/network configuration file.
Change In UID Allocation By default any new users created would get UIDs assigned starting from 1000.This could be changed in /etc/login.defs if required. Default UID assigned to users would start from 500.
This could be changed in /etc/login.defs if required.
Max Supported File Size Maximum (individual) file size = 500TBMaximum filesystem size = 500TB(This maximum file size is only on 64-bit machines. Red Hat Enterprise Linux does not support XFS on 32-bit machines.) Maximum (individual) file size = 16TBMaximum filesystem size = 16TB(This maximum file size is based on a 64-bit machine. On a 32-bit machine, the maximum files size is 8TB.)
File System Check “xfs_repair”XFS does not run a file system check at boot time. “e2fsck”File system check would gets executed at boot time.
Differences Between xfs_repair & e2fsck “xfs_repair”- Inode and inode blockmap (addressing) checks.- Inode allocation map checks.

– Inode size checks.

– Directory checks.

– Pathname checks.

– Link count checks.

– Freemap checks.

– Super block checks.

“e2fsck”- Inode, block, and size checks.- Directory structure checks.

– Directory connectivity checks.

– Reference count checks.

– Group summary info checks.

Difference Between xfs_growfs & resize2fs “xfs_growfs”xfs_growfs takes mount point as arguments. “resize2fs”resize2fs takes logical volume name as arguments.
Change In File System Structure /bin, /sbin, /lib, and /lib64 are now nested under /usr. /bin, /sbin, /lib, and /lib64 are usually under /
Boot Loader GRUB 2Supports GPT, additional firmware types, including BIOS, EFI and OpenFirmwar. Ability to boot on various file systems (xfs, ext4, ntfs, hfs+, raid, etc) GRUB 0.97
KDUMP Supports kdump on large memory based systems up to 3 TB Kdump doesn’t work properly with large RAM based systems.
System & Service Manager “Systemd”systemd is compatible with the SysV and Linux Standard Base init scripts it replaces. Upstart
Enable/Start Service the systemctl command replaces service and chkconfig.- Start Service : “systemctl start nfs-server.service”.

– Enable Service : To enable the service (example: nfs service ) to start automatically on boot : “systemctl enable nfs-server.service”.

Although one can still use the service and chkconfig commands to start/stop and enable/disable services, respectively, they

are not 100% compatible with the RHEL 7 systemctl command (according to redhat).

Using “service” command and “chkconfig” commands.- Start Service : “service start nfs” OR “/etc/init.d/nfs start”

– Enable Service : To start with specific runlevel : “chkconfig –level 3 5 nfs on”

Default Firewall “Firewalld (Dynamic Firewall)”The built-in configuration is located under the /usr/lib/firewalld directory. The configuration that you can customize is under the /etc/firewalld directory. It is not possible to use Firewalld and Iptables at the same time. But it is still possible to disable Firewalld and use Iptables as before. Iptables
Network Bonding “Team Driver”-/etc/sysconfig/network-scripts/ifcfg-team0

– DEVICE=”team0”



– DEVICE=”bond0”

Network Time Synchronization Using Chrony suite (faster time sync compared with ntpd) Using ntpd
NFS NFS4.1NFSv2 is no longer supported. Red Hat Enterprise Linux 7 supports NFSv3, NFSv4.0, and NVSv4.1 clients. NFS4
Cluster Resource Manager Pacemaker Rgmanager
Load Balancer Technology Keepalived and HAProxy Piranha
Desktop/GUI Interface GNOME3 and KDE 4.10 GNOME2
Default Database MariaDB is the default implementation of MySQL MySQL
Managing Temporary Files systemd-tmpfiles (more structured, and configurable, method to manage tmp files and directories). Using “tmpwatch”
References :-

To reboot or not to reboot?

You have patches to apply, we all know that if there are kernel patches that you need to (or at least should) restart/reboot the server.  But what about other packages?  There are a few non-kernel patches which can cause havoc if you spply them and do not reboot the server.  The biggest package that most people miss are libraries, specifically libraries used by the system, like glibc.  When the system is running it loads the libraries it needs into memory, updating does not force a reload of those libraries. Therefore after patching you will have the old version in memory and the new version on disk.  When a new subroutine or kernel process is called it will load the new version into memory, this is where the fun can start.  I say fun because you can see some really strange behavior.  Perhaps you have and in frustration rebooted, problem solved but you are perplexed, well now you know.

Since I deal mostly with Redhat these days here are the packages that require/highly recommend a reboot of the server.  (Caveat: If you can reload what is in memory you do not need to reboot.  This is what we do with services like tomcat or apache after a patch and that removes the old packages from memory and loads the new.)

While we all want to avoid interruptions to system uptime, when updating these packages a reboot is required.  Remember to use your own discretion as this list is provided as an informational guide only.  Redhat could introduce changes that increase or decrease this list.  You may be using packages not considered or functionality not examined.

Red Hat Enterprise Linux 5:

  • kernel
  • kernel-smp
  • kernel-PAE
  • kernel-xen
  • glibc
  • hal

Red Hat Enterprise Linux 6:

  • kernel
  • *-firmware-*
  • glibc
  • hal

Red Hat Enterprise Linux 7:

  • kernel
  • glibc
  • linux-firmware
  • systemd
  • udev

Remember if you don’t have to reboot you should restart the updated service.  Good Luck.

6GB free = 100% disk usage?!

What to do when you have plenty of available disk space but the system is telling you the disk is full?!  I was working on a server migration, moving 94GB of user files from the old server to the new server.  Since we aren’t planning on seeing a lot of growth on the new server, I provisioned a 100GB partition for the user files.  A perfect plan, right?…  So I thought.  After rsync’ing the user files, the new server was showing 100% disk usage:

Filesystem*            Size  Used Avail Use% Mounted on*
                       99G   94G  105M 100% /user_dir

Given competing tasks, at first glance I only saw the 100%.  Naturally I assumed something went wrong with my rsync or I forgot to clear the target partition.  So I deleted everything from the target partition and rsyn’d again.  When the result was the same, it gave my brain pause to say…what?!

My first thought was that the block size was different for the two servers the old server block size was 4kB, perhaps the new server had a larger block size.  As we joked, to much air in the files!  Turns out, using the following commands, the block size was the same on both systems:

blockdev --getbsz partition
# blockdev --getbsz /dev/mapper/my_lv_name 

So the block size of the file system on both servers is 4kB.

I started digging through the man pages of tune2fs and dumpe2fs (and google) to see if I could figure out what was consuming the disk space.  Perhaps there was a defunct process that was holding the blocks )like from a deletion), there wasn’t.  In my research I found the root cause.  New ext2/3/4 partitions set a 5% reserve for file system performance and to insure available space for “important” root processes.  Not a bad idea for the root and var partitions but this approach doesn’t make sense in most other use cases, in this case user data.

Using the tune2fs command we can see what the “Reserved block count” like this:

tune2fs -l /dev/mapper/vg_name-LogVol00

The specific lines we are interested in are:

Block count:              52165632
Reserved block count:     2608282

These lines show that there is a 5% reserve on the disk/Logical Volume.  We fix this with this command:

tune2fs -m 1 /dev/mapper/vg_name-LogVol00

This reduces the reserve to 1%.  The resulting Reserved block count reflects this 1%

Block count:              52165632
Reserved block count:     521107

While this situation is fairly unique, hopefully this will at the least answer your questions and help you better understand the systems you manage.

*The names in the above have been changed to protect the innocent.


Our developers had to have OCI.  Now that I got that out of the way. 😉

We use Oracle as our DB for most applications (calm down, like you couldn’t have figured that out).  In setting up a new application server for a custom application it came to my attention that the application used oci calls.  What a pain to get working on Red Hat!  There is a ton of documentation for Oracle Linux, but that wasn’t an option.  So here is what I had to do to get things working.

yum install php-pecl-apc php-pear gcc php-devel glibc glibc-devel

rpm -iv oracle-instantclient11.2-basic- 
pear download pecl/oci8
tar -xvzf oci8-1.4.10.tgz
./configure --with-oci8=shared,instantclient,/apps/oracleClient/oraInventory/product/11.1.0/client_1
cd oci8-1.4.10
./configure --with-oci8=shared,instantclient,/usr/lib/oracle/11.2/client64
rpm -ivh oracle-instantclient11.2-sqlplus-
echo '/usr/lib/oracle/11.2/client64/lib' > /etc/
yum install php-devel
pecl install oci8-2.0.2.tgz 
echo '' > /etc/php.d/oci8.ini
/etc/init.d/httpd restart

Pain often equals Progress

It has been one of those weeks.  Not fun, to many hours worked, personal events missed, you know the kind of week I am talking about.  If not…what do you do for a living?!

Despite all the pain and stress this week has resulted in Progress, an increased understanding of certain products and new ways to use old tools.  I won’t share the details of my story, just insert yours here, but I will share/document the lessons and commands I learned or rediscovered.  Here we go…

Starting a long running process from home last night around 9PM and forgetting to start screen…priceless!  At 5:30AM this morning the process was still chugging along, with from my calculations would be running for another 18+ hours.  Off to work with no way to grab the terminal (an ssh session), what to do?  Why use strace of course!  Here is how:

strace -pPROCESS_PID -s9999 -e write

ie: strace -p3918 -s9999 -e write

Now even if my ssh session dies at home, I can still see the process output and know when it finishes and if it had any problems.  Yes, I could have piped output to a file, you never forgot anything after working for 15+ hours?

Dealing with a system that had some package inconsistencies and a yum update that failed, followed by a package-utils –cleandupes that erased many complete packages, I thought about using the ‘yum history’ command to revert the system until I read this: “Use the history option for small update rollbacks.”  Here are some of the commands I used which due to the systems package inconsistencies did not perform as expected.

# yum check
# package-cleanup --cleandupes
# yum-complete-transaction
# yum check
# package-cleanup --problems
# rpm -Va --nofiles --nodigest
# yum distribution-synchronizatio

The rest is pretty standard stuff, at least not worth noting in this post.  The end result this week is a lot of lessons learned and a much deeper understanding for an application that I support on my server.  In all, ignoring the backlog, I’d say that is what progress looks like.



The Root of Missing Mail

Like all conscientious system administrator I like to keep tabs on my servers.  One way of doing this is checking root’s email daily.  This is a great idea if you have a few servers and never take vacation!  I manage close to 100 servers, so I need a more efficient way of “hearing” my servers when they complain to root about something.  Aside from monitoring solution (not covered here) the best way to do this is to redirect where email for the root user gets sent.

This seems pretty simple so I never thought of posting about this, until today.  Some facts , to forward mail for the root user leverage the /etc/aliases file.  Like always I added a line to /etc/aliases like this:

# vi /etc/aliases


Ideally you want to set the email address to a list serve so that your backup administrator receives these messages also, so you can take a vacation.

I made that change yesterday on a new server and didn’t give it a second thought.  Today no mail, and I know there was an error on the system?!

First thing I checked was if I could send mail from the server, I could have…or I just forgot because I am sleep deprived…  I was able to send mail from the command line to an email address but not to an alias.  OK, that is a big clue.

While I have never had to do this before, (perhaps I restarted all my other systems?), regardless to fix the problem I simply ran this command:

# newaliases

Bingo, mail started flowing!

If that doesn’t fix it for you, other things to check are:

– Include the following in your /etc/hosts.allow:

ALL: : allow


Yum that was useful!

Pardon the humor.  Just a collection of useful yum commands that are useful to have around but I don’t always remember off the top of my head.  I’ll be adding to this post over time.

How to list the files installed by a yum package

You will need ‘repoquery‘ which is part of ‘yum-utils‘.  If you don’t have ‘repoquery‘ install it first, then start using it:

# yum install yum-utils

# repoquery --list *package*

How to list/install a package from a specific repository

# yum repolist
# yum --disablerepo="*" --enablerepo="repo-name-here" list available
# yum --disablerepo="*" --enablerepo="repo-name-here" install package-name

Update (9/13/13):

Doing an update I ran across this error:

Error:  Multilib version problems found. This often means that the root
       cause is something else and multilib version checking is just
       pointing out that there is a problem. Eg.:
 You could try using --skip-broken to work around the problem
 You could try running: rpm -Va --nofiles --nodigest

Of course the first command that is suggested is a bad idea, I mean talk about denial!  I ran the second, which did nothing, still got the same problem.  So I did a little digging and these two yum commands seem to have corrected the problem, though they do run for a while (10-30 minutes)

# yum check
# yum distro-sync

Update (08 Oct 2015):

Hunting down some system package inconsistencies and I figured out how to list all RPM packages installed from Repo X:

yum list installed | grep @epel