The Geek Diary

Archives for October 2018

Audit rules for monitoring Copy, move, delete and kill Commands In Linux

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System auditing with auditd System auditing is a very important task that should be a part of every server. It allows us to audit minute details related to what exactly is happening within the system. auditd is a userspace component to the Linux auditing system. This means that system users will be able to run […]

“mlock failed: Cannot allocate memory” lvcreate command error in CentOS/RHEL 7

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The Problem When attempting to create an LV the following error occurs. # lvcreate -L 5G -n apps vgOS 7fa0c6cd2000-7fa0c6cd3000 r-xp 00216000 fd:00 8388746 /usr/lib64/libgcc_s-4 .8.5-20150702.so.1: mlock failed: Cannot allocate memory 7fa0c75ce000-7fa0c75cf000 r-xp 00265000 fd:00 8895769 /usr/lib64/libdevmapp er.so.1.02: mlock failed: Cannot allocate memory 7fa0c77d6000-7fa0c77d7000 r-xp 00207000 fd:00 9313347 /usr/lib64/libdevmapp er-event.so.1.02: mlock failed: Cannot allocate memory […]

“Abort command issued nexus” error messages in /var/log/messages file

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The Problem The following log entries are found in /var/log/messages continuously. What do they mean and how to get rid of them? Nov 21 07:08:58 db6foredcd kernel: qla2xxx [0000:49:00.0]-801c:4: Abort command issued nexus=4:3:33 — 1 2002. Nov 21 07:08:58 db6foredcd kernel: qla2xxx [0000:49:00.0]-801c:4: Abort command issued nexus=4:1:33 — 1 2002. Nov 21 07:08:59 db6foredcd kernel: […]

Oracle ASM 12c – New Features with examples

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This post discusses a few 12C ASM new features with examples: Failgroup_repair_time Online disk replace Estimate Work V$ASM_OPERATION view 1. FAILGROUP_REPAIR_TIME For earlier ASM versions, we had disk_repair_time, from 12C onwards we have failgroup_repair_time at the ASM level. Because failure group outages are more likely to be transient in nature and because replacing all the […]

Oracle Database 12c New Feature – RMAN “RECOVER TABLE”

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Table recovery Table recovery was possible in earlier releases as well. Until previous releases, if we wanted to recover a table, we had the following options: Database point in time recovery (DBPITR) Tablespace point in time recovery (TSPITR) Flashback technology The RECOVER TABLE command is a new feature in 12C that allows a point in […]

Interview Questions : Oracle Flex ASM 12c

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What is Oracle Flex ASM? Oracle Flex ASM is an ASM instance which will be running in the cluster based on cardinality defined. The default cardinality is three, but you can change it using srvctl modify asm command. It means that ASM is not required to run on each node in the cluster. In the […]

“comm” Command in Linux with Examples

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It is often useful to compare versions of text files. For system administrators and software developers, this is particularly important. A system administrator may, for example, need to compare an existing configuration file to a previous version to diagnose a system problem. Likewise, a programmer frequently needs to see what changes have been made to […]