Question: How to turn on scsi extended debug messages? What are the field/flag definitions of scsi_logging_level? Additional scsi logging messages can be enabled by writing to /proc/sys/dev/scsi/logging_level either via use of the echo or preferably the sysctl command. The kernel parameter consists of ten packed fields, each 3 bits in length. Each field can have a value of 0 to 7. The higher the field's value, the more verbose the logging of messages associated with that field type. NOTE: … [Read more...] about How to enable additional scsi logging in CentOS/RHEL
chattr Command Examples to Change File Attributes (Make files immutable)
Files can also have attributes that are expressed in another way than the permissions we have seen so far. An example of this is making a file immutable (a fancy word, which means it cannot be changed). An immutable file still has normal ownership and group and RWX permissions, but it will not allow the user to change it, even if it contains the writable permission. Another characteristic of this is that the file cannot be renamed. In this post, we are going to discuss on how to use chattr … [Read more...] about chattr Command Examples to Change File Attributes (Make files immutable)
How to Enable a Database Trigger
Database triggers are PL/SQL code that executes based on event in the database. A trigger is an Oracle statement (or a group of statements enclosed within BEGIN and END statements) that are automatically executed by Oracle in response to any of these statements: ALTER CREATE DROP DELETE INSERT UPDATE The last three are of the greatest interest—triggers that are executed in response to table row changes. How to enable a trigger To enable a database trigger do the following: SQL> … [Read more...] about How to Enable a Database Trigger
When to use rescan-scsi-bus.sh -i (LIP flag) in CentOS/RHEL
The "rescan-scsi-bus.sh" can be used to scan new LUNs in a CentOS/RHEL machine. When 'rescan-scsi-bus.sh -i' is run, script execute as well a LIP_RESET (ISSUE_LIP) which may cause a disruption in I/O on the server and even cause an outage in case of a system running on heavy load. What is LIP (Loop Initialization Protocol)? LIP scans the interconnect and causes the SCSI layer to be updated to reflect the devices currently on the bus. A LIP is, essentially, a bus reset, and will cause device … [Read more...] about When to use rescan-scsi-bus.sh -i (LIP flag) in CentOS/RHEL
How to Disable rpc.quotad Service in CentOS/RHEL 6 and 7
This post explains how to disable rpc.quotad service on CentOS/RHEL 6 or 7 machines. The protocol used by rpc.rquotad is an unsecured and obsolete protocol and should be disabled. Note: This procedure can disrupt NFS clients relying on disk quotas. To avoid issues, schedule a maintenance outage and stop these NFS clients. For CentOS/RHEL 6 or earlier 1. Edit the configuration file /etc/sysconfig/nfs to have an entry which reads RQUOTAD="no". For example: # grep RQUOTAD … [Read more...] about How to Disable rpc.quotad Service in CentOS/RHEL 6 and 7
User Unable To Edit crontab, Error: “/tmp/crontab.Lm34gsJV: Permission denied”
The Problem A non-privileged user cannot edit their crontab file using the command "crontab -e" $ crontab -e no crontab for oracle - using an empty one /tmp/crontab.Lm34gsJV: Permission denied $ The Solution This can happen mainly due to wrong permission on /tmp directory. When a user tries to edit the crontab using 'crontab -e' command, a temporary crontab file is created in /tmp directory, which is overwritten on the actual crontab file when the user saves the changes. Incorrect … [Read more...] about User Unable To Edit crontab, Error: “/tmp/crontab.Lm34gsJV: Permission denied”
showmount Command Examples in Linux
showmount command shows information about an NFS server. This information is maintained by the mountd server on the host. The default value for the host is the value returned by the hostname. With no options, show the clients that have mounted directories from the host. showmount is usually found in /usr/sbin, which is not in the default search path. showmount Command Options The options available with the showmount command are as follows: OptionDescription -a, --allPrint all remote … [Read more...] about showmount Command Examples in Linux
How to Enable Debug Mode for Chronyd Service in CentOS/RHEL 8
What is Chronyd Service In CentOS/RHEL 7 and 8, the operating system's time is set on every boot based on the hardware clock, which is a small-battery driven clock located on the motherboard of your computer. Often, this clock is too inaccurate or has not been set right, therefore it's better to get your system time from a reliable source over the Internet (that uses real atomic time). The chrony daemon, chronyd, sets and maintains system time through a process of synchronization with a remote … [Read more...] about How to Enable Debug Mode for Chronyd Service in CentOS/RHEL 8
How to Recover from a Corrupted or empty /etc/mtab file in CentOS/RHEL 7
Sometimes you may get an error while running the df command saying that tat the /etc/mtab file is either corrupt or empty(removed). It may be a case that someone accidentally edited the /etc/mtab file and has incorrect data. Well, this post will help you restore your correct mtab file. What is the use of /etc/mtab file Before we begin let's see what an mtab file is. /etc/mtab is the file that maintains a list of currently mounted filesystems. So when you run a "df" command, it referes to … [Read more...] about How to Recover from a Corrupted or empty /etc/mtab file in CentOS/RHEL 7
File Access Commands in Linux – find, sort, head, tail
The following file access commands are UNIX commands, not specific shell commands. CommandRemakr findFinds the location of a file sortReads a file and sort the output hear or tailLooks at just the start or end of a file The find Command The find command allows you to search for files and directories and to execute commands on those files. The syntax of the find command has three general argument sections. The paths section is a list of pathnames (directories) to search. The … [Read more...] about File Access Commands in Linux – find, sort, head, tail