- When a Linux machine is powered on BIOS loads up first.
- It will prompt you to select boot device which can be Hard disk, CD-ROM, Floppy drive, Network etc.
- By default generally it will boot with hard disk Next comes your MBR.
- This will load and execute the GRUB boot loader menu.
- GRUB stands for Grand Unified Boot Loader.
- This will display the a splash screen with the contents of /boot/grub/grub.conf.
- List of available and installed kernels will be shown, if not selected default kernel will be loaded
- Kernel: Mounts the root files system as specified by "root=" parameter inside /boot/grub/grub.conf file
- Next it will execute /sbin/init program which will boot the linux machine in the default run level as specified by /etc/inittab
- Runlevel: All the scripts loaded inside the selected runlevel from step 5 will be executed These scripts are placed inside /etc/rc.d/rcx.d/. Here x is the runlevel value which will be varying from 0-6
- Scripts starting from S would load at startup and those starting with K would kill the process at shutdown.
- These incident will take place as per the numerical value assigned to them. For eg: s13network will load prior than s15 sendmail
- Next your login screen will come up
Soft Link
- Using this only a link to the original file is created (shortcut).
- The size of created shortcut is null.
- If you delete the file then the created link (shortcut) won't work.
- In case you delete the shortcut link then it won't affect the original file
- Another copy of the file is created.
- Both the file have same inode no.
- Any changes made in either of the file will appear on the other file.
- Deleting any of the one file won't affect the other file.
# uname -m
# getconf LONG_BIT
4. How can you add a banner or login message in Linux?
By editing these two files
/etc/issue
/etc/motd
5. How will you check the release version of your Linux machine?
# cat /etc/redhat-release
6. What is the difference between normal kernel and kernel-PAE?
kernel in 32 bit machine supports max of 4 GB RAM whereas
kernel PAE in 32 bit linux machine supports till 64 GB RAM
7. Tell me the command to find all the commands in your linux machine having only 2 words like ls, cp, cd etc.
# find /bin /sbin/usr/bin /usr/sbin -name ?? -type f
8. Which file is generally used to configure kickstart?
anaconda.cfg
9. What is the command use to compress a dir using gzip compression?
# tar -czvf myfil.tar.gzip orig_file
10. What is the command use to compress a dir using bzip2 compression?
# tar -cjvf myfil.tar.bzip2 orig_file
11. Which log file will you check for all authentication related messages?
/var/log/secure
12. What is the command to create multiple directories using one command?
Using -p argument along with mkdir command
13. What is the command used to find the process responsible for a particular running file?
# fuser -m filename
# lsof filename
14. What are the three values shown in load average section of top command?
It shows the current, 5 min back and 15 min back load average value
15. How to check all the process running by a particular user?
# ps -u username
16. What is an orphan process?
An orphan process is a process that is still executing, but whose parent has died.
17. How to remove the package without checking the dependencies on Redhat Linux ?
rpm -ev –nodeps package_name
18. What is the command in sar to monitor NIC devices received/transmitted packets?
# sar -n DEV 1 5
19. How to enable SAR command to store data for more then a month?
#/etc/sysconfig/sysstat - Here change the History = 30 days and sar will start storing the data for months.
20. What is ACL?
#Requiremnet to use ACL - A file system should be mounted with ACL option.
#ACL allows us to give permssion to someone without change the actual permission of the file.
# setfacl -m file:rwx -u User
21. How to allow specfic user to login via SSH?
#AllowUsers anze dasa kimy in /etc/sshd/ssh.conf
22. how to create a new partition and add to swap?
#create new parttion with fdisk and mark the partition type as 83
#mkswap /dev/sdaX
#swapon /dev/sdaX
23. How to get the list of dependencies for specific rpm file ?
rpm -qpR rpm_file
24. How to get the list of dependencies for specific package ?
rpm -qR package_name
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