RHCE RHCT Exam: How to mount USB drive on RHEL4

RHCE RHCT Exam: How to mount USB drive on Redhat enterprise Linux server (RHEL4) :

Make Sure USB drive is connnected right to your Linux machine/server , i have plugged in USB thumb drive. Before connecting USB drive do a tail -f /var/log/messages , Redhat Linux sees USB drive as a SCSI device so device will be named as "sdxxx" :
[root@ice ~]# tail -f /var/log/messages
Apr 27 21:52:30 ice kernel: Attached scsi removable disk sdb at scsi1, channel 0, id 0, lun 0
Apr 27 21:52:30 ice kernel: usbcore: registered new driver usb-storage
Apr 27 21:52:30 ice kernel: sdb: assuming drive cache: write through
Apr 27 21:52:30 ice kernel: sdb: sdb1

#df -h
/dev/sdb1 124M 101M 24M 82% /media/usbdisk

USB is mounted as /dev/sdb1

RHCE and RHCT exam:exporting NFS filesystems in RHEL4

Exporting NFS filesystem in RHEL4 (Redhat enterprise Linux) servers:

To export directory /home/export you need to add an entry in /etc/exports :

/home/export parmount.ice.com(rw,sync)

make sure there is space between mount options and hostname otherwise you will get permission error on redhat linux client.

RHCE and RHCT exam: max telnet session limit reached in RHEL4

maximum telnet session limit reached in( RHEL4)Redhat Enterprise Linux :

Quick Fix if you are getting maximum telnet service_limit reached messages in /var/log/secure logs in redhat enterprise Linux servers . Awesome you don't need to reboot your RHEL4 server unlike HP-UX serves :

Getting error : xinetd [4092] :FAIL: telnet service_limit

Just change session limit from 60 for instances to some large number

#
# Simple configuration file for xinetd
#
# Some defaults, and include /etc/xinetd.d/
defaults
{
instances = 400
log_type = SYSLOG authpriv
log_on_success = HOST PID
log_on_failure = HOST
cps = 25 30
}

service telnet2
{
flags = REUSE
socket_type = stream
wait = no
user = root
server = /usr/sbin/in.telnetd
log_on_failure += USERID
disable = no
}

#[root@ice]# service xinetd reload

RHCE RHCT Exam questions : How to check kernel in RHEL4

RHCE RHCT Exam questions : How to check kernel in RHEL4 ?

[root@ice ~]# file /sbin/init
/sbin/init: ELF 32-bit LSB executable, Intel 80386, version 1 (SYSV), for GNU/Linux 2.2.5, dynamically linked (uses shared libs), stripped

RHCE and RHCT exam: Memory available on RHEL4

How can you Check availale Memory on RHEL4 (Redhat Enterprise Linux servers) :

[root@ice /]# grep Mem /proc/meminfo
MemTotal: 255972 kB
MemFree: 5896 kB

RHCE RHCT EXAM :create disk paritions without reboot in RHEL4

Create partition on RHEL :Redhat Enterprise Linux without reboot :

[root@ice ~]# fdisk /dev/sda

The number of cylinders for this disk is set to 2610.
There is nothing wrong with that, but this is larger than 1024,
and could in certain setups cause problems with:
1) software that runs at boot time (e.g., old versions of LILO)
2) booting and partitioning software from other OSs
(e.g., DOS FDISK, OS/2 FDISK)

Command (m for help): p

Disk /dev/sda: 21.4 GB, 21474836480 bytes
255 heads, 63 sectors/track, 2610 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes

Device Boot Start End Blocks Id System
/dev/sda1 * 1 13 104391 83 Linux
/dev/sda2 14 1318 10482412+ 8e Linux LVM
/dev/sda3 1319 1579 2096482+ 82 Linux swap

Command (m for help): n
Command action
e extended
p primary partition (1-4)
e
Selected partition 4
First cylinder (1580-2610, default 1580):
Using default value 1580
Last cylinder or +size or +sizeM or +sizeK (1580-2610, default 2610):
Using default value 2610

Command (m for help): p

Disk /dev/sda: 21.4 GB, 21474836480 bytes
255 heads, 63 sectors/track, 2610 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes

Device Boot Start End Blocks Id System
/dev/sda1 * 1 13 104391 83 Linux
/dev/sda2 14 1318 10482412+ 8e Linux LVM
/dev/sda3 1319 1579 2096482+ 82 Linux swap
/dev/sda4 1580 2610 8281507+ 5 Extended
Command (m for help): w
The partition table has been altered!

Calling ioctl() to re-read partition table.

WARNING: Re-reading the partition table failed with error 16: Device or resource busy.
The kernel still uses the old table.
The new table will be used at the next reboot.
Syncing disks.

Finally type partprobe to make parition change available to Redhat enterprise Linux (RHEL4) without reboot :

[root@ice ~]# partprobe /dev/sda

RHCE and RHCT exam questions

For RHCT and RHCE exam questions, you should know How to check installed packages :

For example to check whether you have firefox installed you can use rpm utility available on RedHat enterprise Linux :
[root@ice ~]# rpm -qa |grep firefox
firefox-1.0.7-1.4.3

RHCT RHCE Exam:DNS name resolution in RHEL4

DNS name resolution in RHEL4 :

/etc/resolv.conf file is used for Domain name resolution (DNS name resolution) :
search rhceexam.linux.com
nameserver 192.168.100.1
nameserver 192.168.100.2

RHCT RHCE Exam:Mounting USB drive on RHEL 4

Mounting USB drive/USB floppy drive on RHEL4

USB drive /device on Redhat Enterprise Linux is recognized as scsi device /dev/sdx (where is x is
number of next available scsi disk... example if you have two scsi disk namely sda and sdb then usb floppy drive will be sdc1

#mount /dev/sdc1 /floppy

RHCT RHCE Exam: practice prepration questions

RHCT RHCE Exam: practice prepration questions :

Question: Where do you look for changing boot loader sequence ?

Answer: on RHEL4 ( redhat enterprise Linux 4 ) /boot/grub/grub.conf

RHCT RHCE Exam: practice prepration questions

RHCT RHCE Exam: practice prepration questions

Question:What file do you edit to set the default runlevel?

Answer: /etc/inittab

RHCT RHCE Exam: practice questions

RHCE RHCT Practice questions of the Day !

Question:How you can check status of network interface ?

Answer : # ifconfig eth0

Number of open files per process in RHEL4 redhat Linux

In RHEL4 (redhat hat enterprise Linux 4 AS ) running kernel 2.6 the number of open files per process is still limited to 1024. you can do ulimit -a to see number of open files per user :

[root@firefox] /# ulimit -a

core file size (blocks) 1000000
data seg size (kbytes) unlimited
file size (blocks) unlimited
max memory size (kbytes) unlimited
stack size (kbytes) 8192
cpu time (seconds) unlimited
max user processes unlimited (1)
pipe size (512 bytes) 8
open files 1024
virtual memory (kbytes) 2105343


To Increases the system limit on open files for instance a process on change the number of open files for Oracle , IB DB2 databases in redhat enterprise Linux (RHEL4) :

#ulimit -n 90000

To make changes permanent add soft and hard limits in /etc/security/limits.conf file :

* soft nofile 90000
* hard nofile 90000

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