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Archives for September 2017

Linux OS Service ‘sysstat’

by admin

Service Name sysstat Description The sysstat service (/etc/init.d/sysstat) is responsible for the regular collection of system performance information. Through the use of cron and sadc (System Activity data collector), sysstat gathers sar data (/var/log/sa/) at 10 minute intervals daily. The service has little impact on overall server performance. The default sysstat configuration (/etc/sysconfig/sysstat) overwrites collected […]

Filed Under: CentOS/RHEL 7, Linux

Linux OS Service ‘microcode_ctl’

by admin

Service Name microcode_ctl Description microcode_ctl updates a microcode in IA32 CPU. The microcode is prepared as a file /etc/firmware/microcode.dat. As this service can fix microcode bugs by updating CPU microcode this should be available.m however only for Intel IA32. Basically, running “service microcode_ctl start” doesn’t start up a daemon, it first checks if the processor […]

Filed Under: Linux, Linux Services

CentOS / RHEL 6 : How to boot into rescue mode

by admin

Rescue mode is the same as a single-user mode. This mode can be used when a condition exists that prevents your system from completing the regular boot process. The system attempts to mount local file systems and start some system services. But rescue mode does not start the network service and does not allow other […]

Filed Under: Linux

CentOS / RHEL 7 : Lock User Account After N Number of Incorrect Login Attempts

by admin

Often a requirement in a secure environment is to lockdown users after they enter a wrong password for a specified number of times. This makes the system protect again The post describes how to lock an account after N incorrect login attempts using pam.d files. The pam_faillock module supports temporary locking of user accounts in […]

Filed Under: CentOS/RHEL 7, Linux

CentOS / RHEL 6 : Lock User Account After N Number of Incorrect Login Attempts

by admin

Often a requirement in a secure environment is to lockdown users after they enter a wrong password for a specified number of times. This makes the system protect againt attacks likes password dictionary attacks. The post describes how to lock an account after N incorrect login attempts using pam.d files. Lock user after N incorrect […]

Filed Under: Linux

CentOS / RHEL 6,7 : How to increase system log message verbosity (rsyslogd)

by admin

The Linux system log daemon is responsible for logging system messages. Starting RHEL 6, The system log daemon/service and its configuration file is rsyslogd – /etc/rsyslog.conf. The post describes how to modify CentOS / RHEL 6,7 system log message verbosity. Verbosity level for rsyslogd Each line in the configuration file /etc/rsyslog.conf defines a rule consisting […]

Filed Under: CentOS/RHEL 7, Linux

CentOS / RHEL : How to exclude kernel or other packages from getting updated using YUM Versionlock Plugin

by admin

Due to application certification and other restrictions in a production environment, it may be preferred to exclude kernel RPM (or other certain RPM) upgrade via yum update. In that case we can use the YUM versionlock plugin to exclude certian packages/rpms from getting updated. Note : The example provided in the post is for the […]

Filed Under: CentOS/RHEL 7, Linux

Beginners guide to Kernel Module Configuration in Linux

by admin

The Linux kernel is loaded into memory by the boot loader. Kernel modules are dynamically loaded and unloaded on demand. They provide device drivers to allow the kernel to access new hardware, support for different file system types and generally extend the functionality of the kernel. Listing the Loaded Kernel Modules To list which kernel […]

Filed Under: CentOS/RHEL 7, Linux

CentOS / RHEL 7 : How to set date, time / NTP and timezone using timedatectl

by admin

RHEL 7 offers another utility to configure and display date and time information, timedatectl. This utility is part of the systemd system and service manager. With the timedatectl command you can : Change the current date and time Set the time zone Configure NTP If you run timedatectl without any options, you would get an […]

Filed Under: CentOS/RHEL 7, Linux

CentOS / RHEL 7 : How to change the verbosity of debug logs during booting

by admin

Removing the rhgb and the quiet kernel command-line parameters, either by editing the /boot/grub/grub.conf file or by using the grub editing mode during boot. Replace these parameters with loglevel and systemd.log_level=debug parameter. This change is generally sufficient to provide as much data as is needed to debug a boot failure. The option rhgb is used […]

Filed Under: CentOS/RHEL 7, Linux

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