By default, if a user logs in a system via bash, all the command history will be saved after exit. How to save every command into ~/.bash_history immediately right after the user type it? How to save all commands typed in a session manually before exit bash? How to Log all Bash History Commands to syslog (/var/log/messages) in CentOS/RHEL How to change the number of commands stored in Bash History UNIX / Linux : Examples of bash history command to repeat last commands CentOS / RHEL : How … [Read more...] about How to save command to history immediately after you type it in bash?
Archives for January 2019
How to Recreate a VDO (Virtual Data Optimizer) index
What is an VDO index VDO uses a high-performance deduplication index called UDS to detect duplicate blocks of data as they are being stored. There are 2 types of UDS indexes available, namely: Sparse UDS index - In general, Red Hat recommends using a sparse UDS index for all production use cases. This is an extremely efficient indexing data structure, requiring approximately one-tenth of a byte of DRAM per block in its deduplication window. Dense UDS index - The default configuration of the … [Read more...] about How to Recreate a VDO (Virtual Data Optimizer) index
How to Increase the Physical Size of a VDO (Virtual Data Optimizer) Volume
If a VDO volume does not have enough physical space, it will send I/O errors to the layers above. The fix for which is to add more physical space to VDO. The VDO physical size is the amount of physical storage VDO can be used to write metadata and user data. Growing the physical size of VDO is often done when planning for growth or if the volume has run out of physical space. VDO volumes are grown online while the volume is active and the operating mode is normal. The command to grow … [Read more...] about How to Increase the Physical Size of a VDO (Virtual Data Optimizer) Volume
How to Configure a Storage Device to Use VDO (Virtual Data Optimizer) Deduplication and Compression
Step 1 - Identify the device for VDO exampansion Identify the storage device that will be used for the VDO volume. Make sure that the storage device is not being used for another purpose. # lsblk NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT sda 8:0 0 119.2G 0 disk ├─sda1 8:1 0 1G 0 part /boot └─sda2 8:2 0 118.2G 0 part ├─rhel-root 253:0 … [Read more...] about How to Configure a Storage Device to Use VDO (Virtual Data Optimizer) Deduplication and Compression
How to Resize (Increase) Logical Size of a VDO (Virtual Data Optimizer) volume in CentOS/RHEL
The logical size or thin-provisioned size of a VDO volume can be grown to a maximum of 4 petabytes. A common reason for doing this is to make more logical space available for file systems and applications. Make sure that if you are using a file system or volume manager above VDO that they are resized, as well. VDO volumes are grown online while the volume is running. The command to grow logically is: # vdo growLogical --name=[vdo volume name] --vdoLogicalSize=[size] Example 1. View the … [Read more...] about How to Resize (Increase) Logical Size of a VDO (Virtual Data Optimizer) volume in CentOS/RHEL
Script To Find Redolog Switch History And Find Archivelog Size For Each Instances In Oracle RAC
This script will list the below items from each instance in the RAC Database. Report the redo log switches on an hourly basis from the all the instances on RAC Database Report the size of the archive logs generated on daily basis from all the instances on RAC Database The same can be used for a Standalone (Non-RAC) Database as well. The script Here is the actual script: /* setting up the environment */ set linesize 200 pagesize 1000 column day format a3 column total format … [Read more...] about Script To Find Redolog Switch History And Find Archivelog Size For Each Instances In Oracle RAC
How to grant a user chown and chmod privileges on a specific directory in Linux
We want to give root privileges to a user. The user is allowed to run the chown and chmod commands on specific files or directories. How this can be allowed? Option #1 You can use group ownership and setgid directories. This allows everyone in the directory group to write to the [PATH] directory, and files created in that directory will be owned by the [PATH] group instead of the primary group of the user who created the file. # chgrp [GROUP] [PATH] # chmod g+ws [PATH] Option #2 1. … [Read more...] about How to grant a user chown and chmod privileges on a specific directory in Linux
How To Add/Remove Locale Archive in CentOS/RHEL 5,6
Occasionally the locale archive file(/usr/lib/locale/locale-archive) does not include a locale you want to use. In this case, you need to create a new locale file, or compile the locale from existent one by: # localedef -f [charmapfile] -i [inputfile] [outputpath] for example: # localedef -f SHIFT_JIS -i ja_JP ja_JP.SJIS The warning message "not ASCII compatible, locale not ISO C compliant" can be ignored. This command can provide appropriate locale even if you get the warning message … [Read more...] about How To Add/Remove Locale Archive in CentOS/RHEL 5,6
How to configure the logging of failed login attempts for vsftpd
Follow the steps outlined below to configure the logging of failed login attempts using pam. 1. Please add to pam_tally2 line after system-auth or password-auth line in /etc/pam.d/vsftpd file as below : auth include password-auth auth required pam_tally2.so deny=5 onerr=fail lock_time=600 serialize account required pam_tally2.so For example : # vi /etc/pam.d/vsftpd #%PAM-1.0 #%PAM-1.0 session optional pam_keyinit.so force revoke auth required pam_listfile.so item=user sense=deny … [Read more...] about How to configure the logging of failed login attempts for vsftpd
How to configure automounter to automount all users’ home directories via NFS in CentOS/RHEL 5,6
1. Edit /etc/auto.master and append the following: # vi /etc/auto.master /home /etc/auto.home 2. Next, create the /etc/auto.home file to specify the NFS server that will house the home directories. In /etc/auto.home two wildcards are being specified. The first one * tells the automounter that it should be prompted to automount all directories underneath the /home/* directory. Next, with the & wildcard the automounter is told that it should use any directory that it can find in the … [Read more...] about How to configure automounter to automount all users’ home directories via NFS in CentOS/RHEL 5,6