The Problem The LVM commands showing below errors: # pvs WARNING: Failed to connect to lvmetad. Falling back to device scanning. >>>> Masked Active: inactive (dead) Sep 08 20:34:29 systemd[1]: Cannot add dependency job for unit lvm2-lvmetad.socket, ignoring: Unit is masked. Sep 08 20:34:32 systemd[1]: Cannot add dependency job for unit lvm2-lvmetad.socket, ignoring: Invalid request descriptor Sep 08 20:34:38 systemd[1]: Cannot add dependency job for unit lvm2-lvmetad.socket, … [Read more...] about “WARNING: Failed to connect to lvmetad. Falling back to device scanning” – error while running LVM commands
CentOS/RHEL 7
CentOS/RHEL: “id” command doesn’t list the Group Name against GID for LDAP Users
The Problem While running "id" command against LDAP users, it only displays the gid for some secondary group and the group name is not being printed: # id user1 uid=48254(user1) gid=100(users) groups=100(users),5002(group1),5001(group2),41257(group3),856(group4),56971 And, the below error was logged in /var/log/sssd/sssd_nss.log : (Tue Mar 14 05:40:09 2020) [sssd[nss]] [nss_cmd_getgrgid_search] (0x0010): getgrgid call returned more than one result !?! The Solution The new group was … [Read more...] about CentOS/RHEL: “id” command doesn’t list the Group Name against GID for LDAP Users
Windows Active Directory Account Shows Inconsistent UID/GID In Different Linux SSSD Clients (CentOS/RHEL)
The Problem The id command shows different UID and GID on different sssd servers for the same Windows Active Directory user. After purging the sssd cache by sss_cache, the UID and GID are still different. 1. Output from one server: # id ad_test_user uid=[UID](ad_test_user) gid=[GID](ad_test_group) groups=[GID](ad_test_group2),[GID](ad_test_group) # sss_cache -u ad_test_user # id ad_test_user uid=[UID](ad_test_user) gid=[GID](ad_test_group) … [Read more...] about Windows Active Directory Account Shows Inconsistent UID/GID In Different Linux SSSD Clients (CentOS/RHEL)
How to Update the hostname in Shell Prompt Once it is Changed in the Linux OS
Question: In this case, the hostname(geeklab) has already been updated in /etc/sysconfig/network and /etc/hosts file, but still needs to be updated in the shell prompt. For example, to change the old shell prompt as below: From : [root@geek ~]# To : [root@geeklab ~]# OS: CentOS/RHEL 6 and 7 Changing the Shell Prompt On the fly The shell prompt is controlled using the PS environment variables. Here is the list of commonly used PS environment variables and their function. PS1 - The … [Read more...] about How to Update the hostname in Shell Prompt Once it is Changed in the Linux OS
How to Recover Deleted rpm Package Files(libraries, configuration files) in CentOS/RHEL 7
Question: Certain system-related files or directories have been erroneously removed/deleted. How to recover them? In this instance, the following system files are missing: - /etc/nsswitch.conf - /lib64/libc.so.6 Identify which system files/directories have been removed The following step relies on the RPM database (rpmdb) to identify missing files and directories. Therefore, the procedure is only applicable for files/directories that are installed via an RPM package. Perform the … [Read more...] about How to Recover Deleted rpm Package Files(libraries, configuration files) in CentOS/RHEL 7
How to Configure NFS Services (server-side) to Run on Static Ports as an Alternative CentOS/RHEL 7
By default, some NFS services (server_side) use well-known ports but some normally just use random ports. The use of random ports does not work so well with strict firewall rules blocking random yet unknown ports. So, sometimes it is best to manually alter or specify static ports for NFS services (server_side) to use. This post describes how to configure NFS services (server-side) to run on static ports as an alternative. Overview NFS services (server-side) include: NLM (NFS lock … [Read more...] about How to Configure NFS Services (server-side) to Run on Static Ports as an Alternative CentOS/RHEL 7
How to blacklist a local disk using the “find_multipaths” directive in CentOS/RHEL 6
After a system reboot, locally attached disks (eg /dev/sda1) are assigned device mapper multipath ("dm-multipath", "dm-mp") names (e.g. /dev/mapper/mpath1p1). Any SCSI device for that matter, which has a scsi ID and is not OPEN/mounted, will be assigned by dm-multipath during boot process unless blacklisted in multipath configuration. Follow the stpes outlined below in order to blacklist a local disk using the "find_multipaths" directive: 1. Find the WWID of the internal drive which you … [Read more...] about How to blacklist a local disk using the “find_multipaths” directive in CentOS/RHEL 6
How to Install NTP Service and Client in CentOS/RHEL 8
In CentOS/RHEL 8, ntp is no longer supported. chrony is enabled by default. For this reason, you might need to migrate from ntp to chrony. Note: In CentOS/RHEL 7 users had a choice to between ntp and chrony. But Starting from CentOS/RHEL 8, they have to use chrony instead of ntp. In standard CentOS/RHEL 8 servers, chrony should be installed and active already. It can be verified by executing: # systemctl status chronyd ● chronyd.service - NTP client/server Loaded: loaded … [Read more...] about How to Install NTP Service and Client in CentOS/RHEL 8
Failed to start LSB: Bring up/down networking – On restarting network service CentOS/RHEL (DHCP client)
The Problem Cannot reliably get networking to start on a server when using DHCP: # sudo /etc/init.d/network restart Restarting network (via systemctl): Job for network.service failed because the control process exited with error code. See "systemctl status network.service" and "journalctl -xe" for details. [FAILED] # journalctl -xe Nov 29 18:57:42 hostaname.domain.com dhclient[37653]: exiting. Nov 29 18:57:42 hostaname.domain.com network[37498]: [FAILED] Nov 29 18:57:42 … [Read more...] about Failed to start LSB: Bring up/down networking – On restarting network service CentOS/RHEL (DHCP client)
How to disable ICMP redirects on CentOS/RHEL
In this post, we will see how to disable ICMP redirect processing, which may help maintain network connectivity in situations where a confused switch or network server shunts traffic away from the selected path. Disable ICMP Redirect From The Command Line ICMP Redirect processing can be turned off until the next reboot via the command line, as shown below. For all network interfaces: # /sbin/sysctl -w net.ipv4.conf.all.accept_redirects = 0 # /sbin/sysctl -w … [Read more...] about How to disable ICMP redirects on CentOS/RHEL