System Admin Q & A – XVII

Ques 1: – What is paged in and paged out ?

Ans: – paged in : In a virtual memory system, memory is described as paged in if it is available in physical memory.

paged out : In a virtual memory system, memory is described as paged out if it is not available in physical memory

Ques 2: – What is SAR and location of SAR log files ?

Ans: – The sar command collect, report, or save UNIX / Linux system activity information. It will save selected counters in the operating system to the /var/log/sa/sadd file. From the collected data, you get lots of information about your server:

CPU utilization
Memory paging and its utilization
Network I/O, and transfer statistics
Process creation activity
All block devices activity

Ques 3: – What is Network Bonding?

Ans: – Bonding is a Linux kernel feature that allows to aggregate multiple like interfaces (such as eth0, eth1) into a single virtual link such as bond0. The idea is pretty simple get higher data rates and as well as link failover.

Ques 4: – What is the Role of luci and ricci in Redhat Cluster Suite ?

Ans: – luci service is the management service that presents the web based cluster interface via https at port 8084 and can be accessed in any browser at “https://”

ricci service is the underlying daemon that helps in cluster configuration sync and file copy, service start, stop etc. and uses tcp port 11111.

Ques 5: – How to Check the NFS Version in UNIX ?

Ans: – Using the nfsstat coomand we can determine the nfs server version. The nfsstat usually displays statistics kept about NFS client and server activity.

Ques 6: – What is the difference between root_squash & no_root_squash

Ans: – root_squash : map root UID/GID to anonymous UID/GID (nobody/nogroup).root_squash will squash the root permissions for the client and denies root access to access/create files on NFS server as root, you get the non-root user permission

no_root_squash : do not map root (nor any other) UID/GID to anonymous UID/GID (nobody/nogroup). no_root_squash will give you the root permission to access/ create files on a NFS Server.

Ques 7: – What is xinetd & why we required xinetd services in linux ?

Ans: – xinetd, the eXtended InterNET Daemon, is an open-source daemon which runs on many Linux and Unix systems and manages Internet-based connectivity.xinetd performs the same function as inetd: it starts programs that provide Internet services. Instead of having such servers started at system initialization time, and be dormant until a connection request arrives, xinetd is the only daemon process started and it listens on all service ports for the services listed in its configuration file. When a request comes in, xinetd starts the appropriate server. Because of the way it operates, xinetd (as well as inetd) is also referred to as a super-server.

Ques 8: – What is use of initrd?

Ans: – The initial RAM disk (initrd) is an initial root file system that is mounted prior to when the real root file system is available. The initrd is bound to the kernel and loaded as part of the kernel boot procedure. The kernel then mounts this initrd as part of the two-stage boot process to load the modules to make the real file systems available and get at the real root file system. The initrd contains a minimal set of directories and executables to achieve this, such as the insmod tool to install kernel modules into the kernel.

Ques 9: – What are Physical Exents; Logical Extents in LVM ?

Ans: – Each physical volume is divided chunks of data, known as physical extents, these extents have the same size as the logical extents for the volume group. Each PV consists of a number of fixed-size physical extents (PEs); similarly, each LV consists of a number of fixed-size logical extents (LEs). (LEs and PEs are always the same size, the default in LVM 2 is 4 MB.) An LV is created by mapping logical extents to physical extents.

Ques 10: – How to find whether you are working physical or virtual linux Server ?

Ans: – Using the command dmidecode we can determine whether I am working on phyical or virtual linux server.

# dmidecode | grep -i -e "kvm" -e "vmware"
Sample Output :

Manufacturer: VMware, Inc.
Product Name: VMware Virtual Platform
Serial Number: VMware-56 4d d3 dd d9 43 5f e4-9d ea c0 99 d0 5e 21 c1
Description: VMware SVGA II

Ques 11: – How to find model & serial number of Linux Servers ?

Ans: – : With help of dmidecode command we find the model & serial number of linux Servers as shown below :

# dmidecode -t system
# dmidecode 2.9
SMBIOS 2.6 present.
Handle 0x0100, DMI type 1, 27 bytes
System Information
Manufacturer: HP
Product Name: ProLiant DL360 G7
Version: Not Specified
Serial Number: USE000A11M
UUID: 30000000-3000-5000-4000-300000000000
Wake-up Type: Power Switch
SKU Number: 579237-B21
Family: ProLiant
Handle 0x2000, DMI type 32, 11 bytes
System Boot Information
Status: No errors detected