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
Linux
3 Ways of Increasing Swap Space on Linux
Sometimes the default physical memory is not enough to serve certain tasks or processes. It may happen that the processes are swapping more memory in and out of the swap space. This post helps to explain how to increase the swap memory on a Linux system. There will be 3 different ways explained in this post, it depends on the availability of each case to use any of these options. Method #1 : Use a new disk 1. Add a new disk to the Linux instance from the available storage. 2. Once the … [Read more...] about 3 Ways of Increasing Swap Space on Linux
How to resize (extend) a partition-based file system in Linux
Note: Resizing a filesystem on a disk parition can be dangerous and can result in loss of data. Make sure you have the backup taken prior to following the steps outlined below. Caveats 1. The filesystem you want to resize must reside on the last partition of the disk. There is no data loss in this case as we recreate the partition without destroying the actual data on it. 2. In case it is not the last partition, you have to destroy the data and recreate a new partition with the desired … [Read more...] about How to resize (extend) a partition-based file system in Linux
Basic “chmod” Command examples in Linux
The Linux command to change permissions on a file or directory is chmod, which we like to read as change file mode. chmod has two operating modes: symbolic mode numeric/octal mode To change permission using the Linux chmod command we have to follow some syntax and rules. As we discussed above we can change permission using Numerical and Alphabetical way, here I have explained both methods with all tricks. Alphabetical Way To use this method you have to remember below rules and … [Read more...] about Basic “chmod” Command examples in Linux
“lsb_release: command not found” – Fix in CentOS/RHEL
The Problem While executing the command "lsb_release -r" to display the release number of the currently installed distribution, user gets below error: # lsb_release -v -bash: lsb_release: command not found How this can be resolved? The Solution To check the RedHat/CentOS version one can use the “lsb_release” command. In most cases, the package providing this command is not installed by default on the systems. To check which package provides the lsb_release command use the below … [Read more...] about “lsb_release: command not found” – Fix in CentOS/RHEL
How to enable the automatic extension for a thin LVM volume
By default, the automatic extension is set to '100' # grep thin_pool_autoextend_threshold /etc/lvm/lvm.conf # Configuration option activation/thin_pool_autoextend_threshold. # thin_pool_autoextend_threshold = 70 thin_pool_autoextend_threshold = 100 These settings imply the function has been disabled. From the /etc/lvm/lvm.conf configuration file: # 'thin_pool_autoextend_threshold' and 'thin_pool_autoextend_percent' define # how to handle automatic pool extension. The former defines … [Read more...] about How to enable the automatic extension for a thin LVM volume
‘nestat -s’ showing a large number for “packet reassembles failed” errors in CentOS/RHEL
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
Linux Interview Questions – Linux Printing (CUPS)
This post covers the most often asked how-to questions about Linux printing support. What tool provides Linux printing support? CUPS, the Common Unix Printing System What kinds of printers can be attached to a Linux system? Linux support printers which are connected using any of the following: Locally Attached Printer (LPT) through a local parallel printer port. Locally Attached Printer (USB) through a local USB port. Remotely Attached Printer (IPP) using the Internet Printing … [Read more...] about Linux Interview Questions – Linux Printing (CUPS)
Server Application Getting “connection refused” From Remote Servers [due to firewalld or iptables] – CentOS/RHEL 7
The Problem An application is getting "connection refused" from other servers. The application is accessible from localhost and also it listens to the expected port. The Solution Firewall on the local server is dropping inbound connection attempts from other servers. Note: By default, CentOS/RHEL 7 uses the FIREWALLD service to manage the IPTABLES rules. The older IPTABLES subsystem is still available and may be used directly if the FIREWALLD service is disabled. 1. Determine if the … [Read more...] about Server Application Getting “connection refused” From Remote Servers [due to firewalld or iptables] – CentOS/RHEL 7
How to make CentOS/RHEL 7 FIPS 140-2 compliant
To make CentOS/RHEL 7 compliant with the Federal Information Processing Standard Publication (FIPS) 140-2, some changes are needed to ensure that the certified cryptographic modules are used and that your system (kernel and userspace) is in FIPS mode. Pre-requisites 1. Confirm that the current openssl version supports fips: # openssl version OpenSSL 1.0.1e-fips 11 Feb 2013 2. Check the output of the following command. It shows if the kernel is already configured for FIPs. It will show … [Read more...] about How to make CentOS/RHEL 7 FIPS 140-2 compliant