RedHat RH302 - RHCE (Redhat Certified Engineer)

Do the following steps as:

1.chmod g+s /data

2.Verify using: ls -ld /data

Permission should be like:

drwxrws--- 2 root sysadmin 4096 Mar 16 18:08 /data

If SGID bit is set on directory then who every users creates the files on directory group owner automatically the owner of parent directory.

To set the SGID bit: chmod g+s directory

To Remove the SGID bit: chmod g-s directory

Do the following steps as:

Login as a root user

cat >schedule.txt

30 05 * * * /bin/echo “Hello”

3. crontab –u david schedule.txt

4. service crond restart

The cron system is essentially a smart alarm clock. When the alarm sounds, Linux runs the commands of your choice automatically. You can set the alarm clock to run at all sorts of regular time intervals. Alternatively, the at system allows you to run the command of your choice once, at a specified time in the future.

Red Hat configured the cron daemon, crond. By default, it checks a series of directories for jobs to run, every minute of every hour of every day. The crond checks the /var/spool/cron directory for jobs by user. It also checks for scheduled jobs for the computer under /etc/crontab and in the /etc/cron.d directory.

Here is the format of a line in crontab. Each of these columns is explained in more detail:

#minute, hour, day of month, month, day of week, command

*        *     *             *      *            command

Entries in a crontab Command Line

Field

Value

Minute

0-59

Hour

Based on a 24-hour clock; for example, 23 = 11 p.m.

Day of month

1-31

Month

1-12, or jan, feb, mar, etc.

Day of week

0-7; where 0 and 7 are both Sunday; or sun, mon, tue, etc.

Command

The command you want to run

Do the following steps as:

1.Create a partition having size 5 GB and change the syste id ‘8e’.

2.use partprobe command

3.pvcreate /dev/hda9Suppose your partition number is hda9.

4.vgextend test0 /dev/hda9vgextend command add the physical disk on volume group.

5.lvextend –L+5120M /dev/test0/lvtestvolume

6.verify using lvdisplay /dev/test0/lvtestvolume.

Do the following steps as:

groupadd training

To create a group we use the groupadd command.

Verify from: cat /etc/group whether group added or not?

Do the following steps as:

1.usermod -G sysuser jackie

2.usermod –G sysuser curtin

3.Verify by reading /etc/group file

Using usermod command we can make user belongs to different group. There are two types of group one primary and another is secondary. Primary group can be only one but user can belongs to more than one group as secondary.

usermod -g groupname usernameTo change the primary group of the user

usermod -G groupname usernameTo make user belongs to secondary group.

Redhat Enterprise Linux 5 Supports the RAID LEVEL 0, RAID LEVEL 1, RAID LEVEL 5 and RAID LEVEL 6 at installation time. You can create it at installation time later no need to type lots of commands for RAID.

At Installation Time:

Create the partitions using diskdruid.

Create the Partitions having File system Type Software RAID.

Click on RAID button

Type the Mount Point

Select File system type

Select RAID Level

Select Partitions/disks as a member of RAID.

Click on ok

After Installation: We can create the RAID Device after Installation on command-line.

Create the Two partitions having equal size. (Specify the Size using Cylinder, find the remaining cylinder and divide by 2).

Change the Partition ID to fd (Linux raid Autodetect) by typing t.

Type wTo write on partitions table.

Use partprobe command to synchronic the partition table.

Use: mdadm --create /dev/md0 --level=1 --raid-devices=2 /dev/hda? /dev/hda?

Verify the RAID: mdadm --detail /dev/md0

mkfs -t ext3 /dev/md0

mount /dev/md0 /data

vi /etc/fstab

/dev/md0/dataext3defaults0 0

Verify mounting devices using mount command.

Do the following steps as:

1.groupadd sysadmin

groupadd command is used to create the group and all group information is stored in /etc/group file.

Do the following steps as:

1.Verify the File whether Shared or not ? : cat /etc/exports

2.Start the nfs service: service nfs start

3.Start the portmap service: service portmap start

4.Make automatically start the nfs service on next reboot: chkconfig nfs on

5.Make automatically start the portmap service on next reboot: chkconfig portmap on

6. Check default firewall is running in your system

# service iptables status

#iptables –F

#service iptables stop

#chkconfig iptables off

6.Verify Either sharing or not: showmount –e localhost

You will see that some shared directory will display

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

By Default system accept the logs only generated from local host. To accept the Log from other host configure:

vi /etc/sysconfig/syslog

SYSLOGD_OPTIONS="-m 0 -r"

Where

-m 0 disables 'MARK' messages.

-r enables logging from remote machines

-x disables DNS lookups on messages recieved with -r

service syslog restart