CentOS/RHEL 5

Question: How to turn on scsi extended debug messages? What are the field/flag definitions of scsi_logging_level? Additional scsi logging messages can be enabled by writing to /proc/sys/dev/scsi/logging_level either via use of the echo or preferably the sysctl command. The kernel parameter consists of ten packed fields, each 3 bits in length. Each field can have a value of 0 to 7. The higher the field's value, the more verbose the logging of messages associated with that field type. NOTE: … [Read more...] about How to enable additional scsi logging in CentOS/RHEL

This post explains how to disable rpc.quotad service on CentOS/RHEL 6 or 7 machines. The protocol used by rpc.rquotad is an unsecured and obsolete protocol and should be disabled. Note: This procedure can disrupt NFS clients relying on disk quotas. To avoid issues, schedule a maintenance outage and stop these NFS clients. For CentOS/RHEL 6 or earlier 1. Edit the configuration file /etc/sysconfig/nfs to have an entry which reads RQUOTAD="no". For example: # grep RQUOTAD … [Read more...] about How to Disable rpc.quotad Service in CentOS/RHEL 6 and 7

The following provides the procedure for configuring and using resource groups under Linux: 1. To use cgroups, you must install the "libcgroup" package on your system. # yum install libcgroup 2. Create a config file for cgroups (/etc/cgconfig.conf) and add below configuration. # vi /etc/cgconfig.conf mount { cpu = /cgroup/cpumem; cpuset = /cgroup/cpumem; memory = /cgroup/cpumem; } # High priority group group mysqldb { cpu { # Allocate the relative share of CPU resources … [Read more...] about How to configure Linux Resource Groups (cgroups) for MySQL

This post explains how to analyse the segfault message in message file and to identify the problem in application or operating system side. What is "segfault"? A segmentation fault (often shortened to segfault) or access violation is a fault raised by hardware with memory protection, to notify operating system (OS) about a memory access violation. The Linux kernel will response it by performing some corrective action, generally passing the fault to the offending process by sending the … [Read more...] about What are “segfault” messages in /var/log/messages file

The Problem rpm commands issue the following error: rpm: error while loading shared libraries: /usr/lib64/liblzma.so.0: invalid ELF header The Solution In this instance, either liblzma.so or the link to it (/usr/lib64/liblzma.so.0) had gotten overwritten. $ rpm -qa | grep binutils rpm: error while loading shared libraries: /usr/lib64/liblzma.so.0: invalid ELF header To resolve this issue, the liblzma.so file and associated soft link need to be restored. Follow the steps outlined below … [Read more...] about rpm: error while loading shared libraries: invalid ELF header

1. Create a directory for you local repository, e.g. /home/mypackage_dir/repository. Move the RPMs into that directory. # mkdir /home/mypackage_dir/repository # cp /media/packages/* /home/mypackage_dir/repo 2. Fix some ownership and filesystem permissions: # chown -R root:root /home/mypackage_dir/repo 3. Install the createrepo package if not installed yet, and run: # createrepo /home/mypackage_dir/repo # chmod -R o-w+r /home/mypackage_dir/repo 4. Create a repository configuration … [Read more...] about How to Create yum Repository in CentOS/RHEL

The Problem The user has set a new value for the parameter global_filter in the /etc/lvm/lvm.conf file. After setting the parameter value 'vgs' command gives below error: # vgs Configuration setting "global/global_filter" unknown. ... The Solution User has put the "global_filter" parameter under the 'global {}' section in /etc/lvm/lvm.conf configuration file. global { ... global_filter = [ "r/.*/" ] ... } Perform the following steps to solve the LVM filter issue: 1. Take … [Read more...] about CentOS/RHEL – vgs command reports error: “global/global_filter” unknown

The Problem System exhibits some performance degradation. Checking with netstat shows very large (and rising) numbers of "packet reassembles failed" similar to: # netstat -s | fgrep reassembles 353357449 packet reassembles failed 353359152 packet reassembles failed 353360314 packet reassembles failed 353361547 packet reassembles failed 353363020 packet reassembles failed 353364064 packet reassembles failed The Solution In general, IP packet reassembles may fail if: There is not … [Read more...] about ‘nestat -s’ showing a large number for “packet reassembles failed” errors in CentOS/RHEL

The Problem While executing: # yum update The following error occurs: One of the configured repositories failed (Unknown), and yum doesn't have enough cached data to continue. At this point the only safe thing yum can do is fail. There are a few ways to work "fix" this: 1. Contact the upstream for the repository and get them to fix the problem. 2. Reconfigure the baseurl/etc. for the repository, to point to a working upstream. This is most often useful if you are using a … [Read more...] about “Could not resolve proxy: https; Unknown error” – error with ‘yum update’