Posts Categorized: red hat centos

Resetting Root Password in Single User Mode

Using Red Hat  / CentOS etc one method of resetting the root user password is to boot into single user mode. To do so, interrupt the booting process if necessary so that you see the Grub boot menu: Press the ‘e‘ keyboard button to edit the boot parameters. You will see a menu with the… Read more »

Gitlab Bulk Update can_create_group

I had been allowing normal users to create groups within Gitlab but subsequently discovered some confusion among users between groups and projects. Some users had been creating a group with a single project when a project with multiple members was more suitable. A decided to update the Gitlab CE database to amend the users table… Read more »

sssd ldap: No Group Members shown

Openldap group

With several machines configured to use OpenLdap for user and group authentication/permissions I was having the problem that the getent and id commands were not returning all the group information. My groups exist in the Ldap directory with members listed under ‘memberuid’ but when entering:

I was getting:

when I should have been… Read more »

Bleeding Edge PHP on CentOS 7

The PHP packages in the base / epel repositories are very conservative. To opt for something more current the REMI repo can be used. Install the remi-release package (info)  first:

This will create the remi specific repo files in the /etc/yum.repo.d directory, specifically:

To install later PHP versions alongside your current PHP version… Read more »

Discourse CentOS – which: no in

This must be my second or third attempt at Discourse having given up several times before and I may well find reasons to avoid it again. The Discourse advice of just use Ubuntu or using DigitalOcean doesn’t cut it for me. One of the problems I ran into today (after following these docker/discourse instructions) was… Read more »

Resetting Drained Slurm Node

After barking up the wrong tree for a while I discovered via StackExchange how to reset a Slurm Node reporting as drained. Run the scontrol command then update the node as shown in the following example commands (amend the word jacob here to the name of your node):


CentOS 7 as NAT Gateway for Private Network

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The scenario is a small private network connected via a switch and using 192.168.0.* addresses. One of the machines (let’s call it RTR001) on the network has two network interface cards. One with an address on the 192.168.0.* network and another providing wider network (& internet) access on a 123.111.123.* network. This machine (RTR001) will… Read more »

Building Likwid RPMs for CentOS

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Installing likwid is easy (using ./configure, make, make install) however I wanted to create an RPM package to allow for repeatable builds and installation across a number of nodes/machines. With the ‘Development Tools’ package installed I started with:

I downloaded the latest likwid release (3.1.3) and copied it to

Then moved to the… Read more »

Huge Pages in CentOS 6

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To check the size and amount of Huge Pages use:

This should so something like:

To change the number of HugePages use the following:

This would allocate 2560x2048kB = 5GB

To check the impact on memory:

Reset Huge Pages The change can be applied permanently in /etc/sysctl.conf but to… Read more »

Building Slurm Scheduler RPM Packages

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Download the slurm tarball from Install dependencies:

Build the RPM:

After 5 minutes compiling this will create RPMs in the directory: ~/rpmbuild/RPMS/x86_64/ for me this was /root/rpmbuild/RPMS/x86_64/ The created RPMs were as follows: slurm-14.03.10-1.el6.x86_64.rpm slurm-pam_slurm-14.03.10-1.el6.x86_64.rpm slurm-sjobexit-14.03.10-1.el6.x86_64.rpm slurm-slurmdb-direct-14.03.10-1.el6.x86_64.rpm slurm-devel-14.03.10-1.el6.x86_64.rpm slurm-perlapi-14.03.10-1.el6.x86_64.rpm slurm-sjstat-14.03.10-1.el6.x86_64.rpm slurm-sql-14.03.10-1.el6.x86_64.rpm slurm-munge-14.03.10-1.el6.x86_64.rpm slurm-plugins-14.03.10-1.el6.x86_64.rpm slurm-slurmdbd-14.03.10-1.el6.x86_64.rpm slurm-torque-14.03.10-1.el6.x86_64.rpm I then added these RPM files to… Read more »