The Network Information Service consists of a client-server directory service protocol for distributing system configuration data such as user and host names between computers. NIS enables you to create user accounts that can be shared across all systems on your network. The description of NIS daemons are given below: portmap/rpcbind: The foundation RPC daemon upon […]
CentOS/RHEL 6
How To Disable Weak Cipher And Insecure HMAC Algorithms in SSH services for CentOS/RHEL 6 and 7
This post will show how to Disable the HMAC MD5 and the CBC ciphers as an example for CentOS/RHEL 6 and 7. For CentOS/RHEL 7 For more information please look at the man pages: # man sshd_config Ciphers Specifies the ciphers allowed. Multiple ciphers must be comma-separated. If the specified value begins with a ‘+’ […]
“Server refused to allocate pty” – Unable to login to CentOS/RHEL
The Problem On an CentOS/RHEL 6 server, all logins started to fail to the system with the following errors: Server refused to allocate pty /etc/profile: line 48: /dev/null: Permission denied /etc/profile: line 76: /dev/n ull: Permission denied /etc/profile: line 76: /dev/null: Permission denied /etc/pr ofile: line 76: /dev/null: Permission denied /etc/profile: line 76: /dev/null: Permission […]
“not enough to start the array” – error while staring mdadm RAID array
The Problem After replacing issue disk on software RAID, mdadm Fails to Start the RAID Array with Error – “not enough to start the array” and Software Raid State is showing “active, FAILED, Not Started” “mdadm –detail /dev/md0” showing only 4 disks are active and 8 removed disks. # mdadm –detail /dev/md0 State : active, […]
“Connection reset by peer” – error while ssh into a CentOS/RHEL system with a specific user only
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 […]
“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 […]
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 […]
“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 […]
“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. […]
“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 […]