Fedora

Unlike most monitoring tools that either focus on a small set of statistics, format their output in only one way, run either interactively or as a daemon but not both, collectl tries to do it all. You can choose to monitor any of a broad set of subsystems which currently include buddyinfo, cpu, disk, inodes, InfiniBand, lustre, memory, network, nfs, processes, quadrics, slabs, sockets and tcp. Installing collectl The collectl community project is maintained at … [Read more...] about Troubleshooting performance issue in CentOS/RHEL using collectl utility

The Name Service Caching Daemon (nscd) is a service that runs in the background and keeps a copy of /etc/passwd, /etc/group, and /etc/hosts files in /var/db/nscd/ directory. This can aid performance by reducing disk read overhead on a heavily loaded system dealing with many logins or name resolution requests. # pwd /var/db/nscd # ll total 648 -rw------- 1 root root 217016 Oct 22 11:14 group -rw------- 1 root root 217016 Oct 22 11:09 hosts -rw------- 1 root root 217016 Oct 22 11:14 … [Read more...] about What is the nscd service and how is it used in CentOS/RHEL

We no longer intend to use the native RedHat multipathing or dm-multipathing. How can we disable it permanently so that it can not be enabled automatically upon reboot? To disable the native multipathing on a CentOS/RHEL 6,7 system follow the steps outlined below: 1. Edit /etc/multipath.conf and edit the blacklist{} section: # vi /etc/multipath.conf blacklist { devnode * } 2. Stop multipathd and chkconfig daemon off: ### For CentOS/RHEL 6 ### # service multipathd stop # … [Read more...] about How to disable native multipath (dm-multipath) in CentOS/RHEL

Red Hat Enterprise Linux provides audit rules feature to log the file activities done by users or processes. This can be achieved by configuring audit rules. This post particularly focuses on monitoring file deletions by users or process on a Linux system. Follow the steps outlined below to configure auditd rules for monitoring file deletion in a CentOS/RHEL system. Steps for CentOS/RHEL 4,5,6 1. To configure audit rules, add the following line in /etc/audit.rules file (for RHEL 5,6 use the … [Read more...] about How to monitor who is deleting a file in CentOS/RHEL using auditd

This post will provide an example of the NIS configuration procedures. This will include which packages are needed for a NIS server and client and the procedures for configuration of both server and client. Setting up a NIS Server The packages that are required for setting up a NIS Server are: ypserv ypbind portmap yp-tools It is possible to check whether the following packages are installed on the system using the command rpm -q [package-name], e.g. # rpm -q ypserv ypbind … [Read more...] about How to configure a NIS server and client in CentOS/RHEL/Fedora

There are 2 ways in which this can be accomplished. 1. Using /etc/fstab 2. Using a Systemd Mount Unit File 1. Using /etc/fstab After device creation, the filesystem must be added to the /etc/fstab file to persistently mount. Below is an example /etc/fstab entry for a VDO device: # vi /etc/fstab # # /etc/fstab # Created by anaconda on Tue Nov 27 17:58:51 2018 # # Accessible filesystems, by reference, are maintained under '/dev/disk/'. # See man pages fstab(5), findfs(8), mount(8) … [Read more...] about How to Configure VDO (Virtual Data Optimizer) filesystem to Persistently Mount at Boot

The big issue that may act as a potential deal breaker is the need to maintain user accounts on the RHEL server and the AD domain to which the workstation accessing the server belongs. If we implement more than one server, the problem is exacerbated with the need for accounts on each and every server as well as the AD domain. The simple solution is to incorporate the RHEL server into the AD domain and use AD accounts for resource access. In this way, we can use a single sign-on to the Active … [Read more...] about How to Join Active Directory domain using adcli from a CentOS/RHEL system

iSCSI (Internet Small Computer System Interface) is a network storage solution based on the communication protocol provided by SCSI. To understand iSCSI, you first need to know about some key terms: Target — This term describes the storage device, which resides on a server. The server can either be on a LAN (Local Area Network) or a WAN (Wide Area Network). Think of the target as the storage device being shared. Also, keep in mind that a target is actually considered a device, not a … [Read more...] about How to configure the iscsi-initiator in CentOS/RHEL 6,7

There is no such an option which can limit the maximum connections of ssh. But as a workaround, we can make sshd be controlled by xinetd super daemon and use instances option of xinetd to limit the maximum connections of ssh. In most Unix-like operating systems, the OpenSSH server runs as a daemon, listening for SSH connections. On CentOS/RHEL systems, however, sshd is controlled by the super-server daemon, xinetd. Whenever an SSH client attempts to contact sshd on TCP port 22, xinetd notices … [Read more...] about How to limit maximum ssh connections in CentOS/RHEL