This is boot related problem. There will be same questions repeated two times but problem is different.

First When you restart the system you will get the Error:

mount: error 15 mounting ext3

mount: error 2 mounting none

switchroot: mount failed: 22

umount /initrd/dev/: 2

Kernel Panic: no syncing: Attempted to kill init !

This error occurred in your system before showing welcome redhat linux. That means problem in grub boot loader.

Restart the System

Check the grub boot loader configuration by pressing e shortcut key.

You will see like:

root (hd0,0)

kernel /vmlinuz-2.6.9-5.EL ro root= / rhgb quiet

initrd /initrd-2.6.9-5.EL.img

OR

root (hd0,0)

kernel /vmlinuz-2.6.9-5.EL ro root=LABEL=/root rhgb quiet

initrd /initrd-2.6.9-5.EL.img

Then Edit Boot loader to make like

root (hd0,0)

kernel /vmlinuz-2.6.9-5.EL ro root=LABEL=/ rhgb quiet

initrd /initrd-2.6.9-5.EL.img

Check all lines and edit as same as above. Press b to boot the system

After booting the system you should correct the /etc/grub.conf file.

This is boot related problem. There will be same questions repeated two times but problem is different.

First When you restart the system you will get the Error:

File Not Found

mount: error 15 mounting ext3

mount: error 2 mounting none

switchroot: mount failed: 22

umount /initrd/dev/: 2

Kernel Panic: no syncing: Attempted to kill init !

This error occurred in your system before showing welcome redhat linux. That means problem in grub boot loader.

Restart the System

Check the grub boot loader configuration by pressing e shortcut key.

You will see like:

root (hd0,0)

kernel /vmlinuz-2.6.9-5.EL ro root= / rhgb quiet

initrd /initrd-2.6.9-5.EL.img

OR

root (hd0,0)

kernel /vmlinuz-2.6.9-5.EL ro root=LABEL=/root rhgb quiet

initrd /initrd-2.6.9-5.EL.img

Then Edit Boot loader to make like

root (hd0,0)

kernel /vmlinuz-2.6.9-5.EL ro root=LABEL=/ rhgb quiet

initrd /initrd-2.6.9-5.EL.img

Check all lines and edit as same as above. Press b to boot the system

After booting the system you should correct the /etc/grub.conf file.

If still you are getting Error like File not found , it seems that either kernel file or initrd file is missing. To troubleshoot with these problem, boot the system on rescue mode.

linux rescue

chroot /mnt/sysimage

Check the files on /boot, if not available install the kernel package from ftp or nfs server

Create the initrd image file on boot using: mkinitrd initrd-2.6.9-5.EL.img `uname –r`

To understand the role of a boot loader, take a step back from Linux. When you boot your computer, the BIOS starts by detecting basic hardware, including your hard drives. Once it's done, it looks for the boot loader on the Master Boot Record of the first available disk. If you're working with an older PC, the BIOS can't find your boot loader unless it's located within the first 1,024 cylinders of the hard disk.

Newer BIOSes overcome this problem with Logical Block Addressing, which is also known as LBA mode. LBA mode reads 'logical' values for the cylinder, head, and sector, which allows the BIOS to 'see' a larger disk drive.

If you have multiple hard drives, there is one more caveat. If your drives are IDE hard drives, the /boot directory must be on a hard drive attached to the primary IDE controller. If your drives are all SCSI hard drives, the /boot directory must be located on a hard drive with SCSI ID 0 or ID 1. If you have a mix of hard drives, the /boot directory must be located on either the first IDE drive or a SCSI drive with ID 0. In other words, this is not an issue on the Red Hat exams unless the computer that you're tested on has more than two hard drives. And I believe that's less likely, as that would increase the cost of the exam.

If you are getting the Kernel panic error, it means it is boot loader related problem. Redhat Enterprise Linux uses the GRUB boot loader. You can pass the kernel parameter from the boot loader as well as you can correct the kernel parameter passing from boot loader from GRUB screen at boot time.

GRUB boot loader configuration file is: /etc/grub.conf

And Correct Configuration is:

default=0

timeout=5

splashimage=(hd0,0)/grub/splash.xpm.gz

hiddenmenu

title Red Hat Enterprise Linux ES (2.6.9-5.EL)

root (hd0,0)

kernel /vmlinuz-2.6.9-5.EL ro root=LABEL=/ rhgb quiet

initrd /initrd-2.6.9-5.EL.img

Probably miss-configured the boot loader, so giving this problem. You can pass the correct parameter from GRUB prompt:

Table 3-3: GRUB Editing Commands

Command

Description

b

Boot the currently listed operating system

d

Delete the current line

e

Edit the current line

o

Create an empty line underneath the current line

O

Create an empty line above the current line

If you know all parameters and sequence of the boot loader you can enter in command prompt also.

Press c on GRUB screen.

Grub > root (hd0,0)

grub > kernel /vmlinuz-2.6.9-5.EL ro root=LABEL=/ rhgb quiet

grub > initrd /initrd-2.6.9-5.EL.img

grub > boot

Do the following steps as:

Quotas are used to limit a user's or a group of users' ability to consume disk space. This prevents a small group of users from monopolizing disk capacity and potentially interfering with other users or the entire system. Disk quotas are commonly used by ISPs, by Web hosting companies, on FTP sites, and on corporate file servers to ensure continued availability of their systems.

Without quotas, one or more users can upload files on an FTP server to the point of filling a filesystem. Once the affected partition is full, other users are effectively denied upload access to the disk. This is also a reason to mount different filesystem directories on different partitions. For example, if you only had partitions for your root (/) directory and swap space, someone uploading to your computer could fill up all of the space in your root directory (/). Without at least a little free space in the root directory (/), your system could become unstable or even crash.

You have two ways to set quotas for users. You can limit users by inodes or by kilobyte-sized disk blocks. Every Linux file requires an inode. Therefore, you can limit users by the number of files or by absolute space. You can set up different quotas for different filesystems. For example, you can set different quotas for users on the /home and /tmp directories if they are mounted on their own partitions.

Limits on disk blocks restrict the amount of disk space available to a user on your system. Older versions of Red Hat Linux included LinuxConf, which included a graphical tool to configure quotas. As of this writing, Red Hat no longer has a graphical quota configuration tool. Today, you can configure quotas on RHEL only through the command line interface.

1. vi /etc/fstab

/dev/hda11 /data ext3 defaults,usrquota 1 2

2. Either Reboot the System or remount the partition.

Mount –o remount /dev/hda11 /data

3. touch /data/aquota.user

4. quotacheck –ufm /data

5. quotaon -u /data

6. edquota –u user1 /data

and Specified the Soft limit and hard limit on opened file.

To verify either quota is working or not:

Soft limit specify the limit to generate warnings to users and hard limit can’t cross by the user. Use the quota command or repquota command to monitor the quota information.

Do the following steps as:

Use fdisk /dev/hda  To create new partition.

Type n  For New partitions

It will ask for Logical or Primary Partitions. Press l for logical.

It will ask for the Starting Cylinder: Use the Default by pressing Enter Key.

Type the Size: +100M  You can Specify either Last cylinder of Size here.

Press P to verify the partitions lists and remember the partitions name.

Press w to write on partitions table.

Either Reboot or use partprobe command.

Use mkfs –t ext3 /dev/hda?

Or

mke2fs –j /dev/hda?  To create ext3 filesystem.

vi /etc/fstab

Write:

/dev/hda? /data ext3 defaults 0 0

11. Verify by mounting on current Sessions also:

mount /dev/hda? /data

You should know about the /etc/inittab file, where default runlevel will define. And Much more runlevel specific Scripts are called here.

Actually that problem will occur if you don’t specify the default runlevel.

Reboot the system

Boot the System on single user mode.

Except for a normal boot of Linux, single-user mode is the most commonly used option. This is the system maintenance mode for experienced Linux administrators. It allows you to perform clean backups and restores to any partitions as needed from local hardware. It also allows you to run administration commands, recover or repair password and shadow password files, run filesystem checks, and so forth.

vi /etc/inittab and Write

id:runlevel:initdefault:

Standard Runlevels in RedHat Enterprise Linux

Runlevel

Description

0

Halt

1

Single-user mode, for maintenance (backups/restores) and repairs

2

Multiuser, without networking

3

Multiuser, with networking

4

Unused

5

X11, defaults to a GUI login screen. Logins bring the user to a GUI desktop.

6

Reboot (never set initdefault in /etc/inittab to this value!)

It is due to either default runlevel or runlevel specific scripts.

id:?:initdefault:  Where default runlevel is specified. It shouldn’t be 6.

l3:3:wait:/etc/rc.d/rc 6  It reads the scripts of runlevel 6 while booting system on rulevel 3.

It should be like:

si::sysinit:/etc/rc.d/rc.sysinit

l0:0:wait:/etc/rc.d/rc 0

l1:1:wait:/etc/rc.d/rc 1

l2:2:wait:/etc/rc.d/rc 2

l3:3:wait:/etc/rc.d/rc 3 Should be like this

l4:4:wait:/etc/rc.d/rc 4

l5:5:wait:/etc/rc.d/rc 5

l6:6:wait:/etc/rc.d/rc 6

Do the following steps as:

hostname station?.example.com  This will set the host name only for current session. To set hostname permanently.

vi /etc/sysconfig/network

HOSTNAME=station?.example.com

service network restart

Do the following steps as:

1. /proc is the virtual filesystem, we use /proc to modify the kernel parameters at running time.

# echo “1” > /proc/sys/net/ipv4/ip_forward

2. /etc/sysctl.conf  when System Reboot on next time, /etc/rc.d/rc.sysinit scripts reads the file /etc/sysctl.conf. To enable the IP forwarding on next reboot also you need to set the parameter.

net.ipv4.ip_forward=1

Here 0 means disable, 1 means enable.

Do the following steps as:

1. Use fdisk /dev/hda  To create new partition.

Type n  For New partition

It will ask for Logical or Primary Partitions. Press l for logical.

It will ask for the Starting Cylinder: Use the Default by pressing Enter Key.

Type the Size: +100M  You can Specify either Last cylinder of Size here.

Press P to verify the partitions lists and remember the partitions name. Default System ID is 83 that means Linux Native.

Type t to change the System ID of partition.

Type Partition Number

Type 82 that means Linux Swap.

Press w to write on partitions table.

Either Reboot or use partprobe command.

mkswap /dev/hda?  To create Swap File system on partition.

swapon /dev/hda?  To enable the Swap space from partition.

free –m  Verify Either Swap is enabled or not.

vi /etc/fstab

/dev/hda? swap swap defaults 0 0

Reboot the System and verify using free command that swap is automatically enabled or not.