The Problem When trying to open an ssh connection to a system with a specific account, it failed with 'Connection reset by peer'. Other users can successfully connect with ssh to this system. Below is an example showing the failed login to node [NODE2] with the account 'oracle'. [oracle@NODE1]$ ssh oracle@[NODE2] oracle@[NODE2]'s password: Read from remote host [NODE2]: Connection reset by peer Connection to [NODE2] closed. [oracle@NODE1]$ ssh root@[NODE2] root@[NODE2]'s … [Read more...] about “Connection reset by peer” – error while ssh into a CentOS/RHEL system with a specific user only
CentOS/RHEL 6
“Couldn’t authenticate with keytab while discovering which salt to use: hostname: KDC has no support for encryption type” – error while joining domain
The Problem A CentOS/RHEL 6 client fails to be enrolled in an Active Directory domain, with the adcli command randomly failing with the following error written to the console: Couldn't authenticate with keytab while discovering which salt to use: [SERVER$@DOMAIN_NAME]: KDC has no support for encryption type The following errors are logged at the same time to /var/log/messages: Feb 20 16:23:52 [hostname] [sssd[ldap_child[27134]]]: Failed to initialize credentials using keytab … [Read more...] about “Couldn’t authenticate with keytab while discovering which salt to use: hostname: KDC has no support for encryption type” – error while joining domain
How to Switch Back To Previous Version of openjdk in CentOS/RHEL
Question: How to downgrade the Java version which got installed/updated during system patching? The "java" command does not run the JVM that has been installed. Java applications can fail to run if an unexpected Java Runtime Environment is found. Recent version is - java-1.8.0-openjdk-1.8.0.51-1.b16.el6_7.x86_64 Required version is - java-1.7.0-openjdk-1.7.0.85-2.6.1.3.0.1.el6_7.x86_64 # rpm -qa | grep -i openjdk java-1.8.0-openjdk-1.8.0.51-1.b16.el6_7.x86_64 … [Read more...] about How to Switch Back To Previous Version of openjdk in CentOS/RHEL
“Device /dev/mappper/mpath25 Not Found (or Ignored By Filtering)” – error while creating physical volume with pvcreate
The Problem When trying to create physical volume , getting the below error error: # pvcreate /dev/mappper/mpath25 Device /dev/mappper/mpath25 not found (or ignored by filtering). The issue can be reproduced at will with the following step: # pvcreate /dev/mappper/mpath25 The Solution Upon checking it was found that start sector was not zeroed out. # pvcreate /dev/mappper/mpath25 Device /dev/mappper/mpath25 not found (or ignored by filtering). # fdisk -l … [Read more...] about “Device /dev/mappper/mpath25 Not Found (or Ignored By Filtering)” – error while creating physical volume with pvcreate
“Read-only locking type set. Write locks are prohibited. Can’t get lock for [volume group]” – error during lvextend
The Problem Unable to extend LVM filesystem. The following error message is received on running the lvextend command: Read-only locking type set. Write locks are prohibited. Can't get lock for rootvg resize2fs 1.43-WIP (20-Jun-2013) The filesystem is already 1310720 blocks long. Nothing to do! The Solution The parameter locking_type is set to 4 in /etc/lvm/lvm.conf. # grep locking lvm.conf |grep -v '#' "lvmetad", "metadata", "cache", "locking" ] locking_type = 4 … [Read more...] about “Read-only locking type set. Write locks are prohibited. Can’t get lock for [volume group]” – error during lvextend
“WARNING: Failed to connect to lvmetad. Falling back to device scanning” – error while running LVM commands
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: “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 Generate An CentOS/RHEL 6 UEFI Bootable ISO Image
1. Mount CentOS/RHEL 6.9 installation iso into /media/RHEL6.9; # mkdir /media/RHEL6.9 # mount -o ro /dev/cdrom /media/RHEL6.9 2. Create a new folder /opt/make_iso; # mkdir /opt/make_iso 3. Copy all files of CentOS/RHEL 6.9 installation iso to /opt/make_iso; # tar cf - /media/RHEL6.9 | ( cd /opt/make_iso/; tar xpvf - ) 4. Copy uefi kickstart config file to the root directory of iso image: # cp uefi_ks.cfg /opt/make_iso/ks.cfg 5. Copy efiboot.img to the root directory of iso … [Read more...] about How To Generate An CentOS/RHEL 6 UEFI Bootable ISO Image
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