System Admin Q & A – I

Ques 1: – What is the difference between LILO and GRUB ?

1) LILO has no interactive command interface, whereas GRUB does.

2) LILO does not support booting from a network, whereas GRUB does.

3) LILO stores information regarding the location of the operating systems it can to load physically on the MBR.

If you change your LILO config file, you have to rewrite the LILO stage one boot loader to the MBR. Compared with GRUB, this is a much more risky option since a misconfigured MBR could leave the system unbootable. With GRUB, if the configuration file is configured incorrectly, it will simply default to the GRUB command-line interface.

Ques 2: – What is LVM Snapshot ?

An LVM snapshot is an exact copy of an LVM partition that has all the data from the LVM volume from the time the snapshot was created. The big advantage of LVM snapshots is that they can be used to greatly reduce the amount of time that your services/databases are down during backups because a snapshot is usually created in fractions of a second. After the snapshot has been created, you can back up the snapshot while your services and databases are in normal operation.

Ques 3: – What is the meaning of Hard & soft mount option in NFS server ?

Hard mount

– If the NFS file system is hard mounted, the NFS daemons will try repeatedly to contact the server. The NFS daemon retries will not time out, will affect system performance, and you cannot interrupt them

Soft mount

– If the NFS file system is soft mounted, NFS will try repeatedly to contact the server until either:

A connection is established
The NFS retry threshold is met
The nfstimeout value is reached

Ques 4: – How to verify the signature of an rpm ?

rpm -K test-1.0-1.i386.rpm

Ques 5: – What is an inode ?

An inode is a data structure on a traditional Unix-style file system such as UFS. An inode stores basic information about a regular file, directory, or other file system object.

When a file system is created, data structures that contain information about files are created. Each file has an inode and is identified by an inode number (often “i-number” or even shorter, “ino”) in the file system where it resides. Inodes store information on files such as user and group ownership, access mode (read, write, execute permissions)

and type of file. There is a fixed number of inodes, which indicates the maximum number of files each filesystem can hold.

Ques 6: – State some of the products of Sybase?

udev is the device manager for the Linux 2.6 kernel series. Primarily, it manages device nodes in /dev. It is the successor of devfs and hotplug, which means that it handles the /dev directory and all user space actions when adding/removing devices, including firmware load.

Ques 7: – What is the difference between ext2 and ext3 file systems?

The ext3 file system is an enhanced version of the ext2 file system.

The most important difference between Ext2 and Ext3 is that Ext3 supports journaling.
After an unexpected power failure or system crash (also called an unclean system shutdown), each mounted ext2 file system on the machine must be checked for consistency by the e2fsck program. This is a time-consuming process and during this time, any data on the volumes is unreachable. The journaling provided by the ext3 file system means that this sort of file system check is no longer necessary after an unclean system shutdown. The only time a consistency check occurs using ext3 is in certain rare hardware failure cases, such as hard drive failures. The time to recover an ext3 file system after an unclean system shutdown does not depend on the size of the file system or the number of files; rather, it depends on the size of the journal used to maintain consistency. The default journal size takes about a second to recover, depending on the speed of the hardware.

For testing a new apache version before moving your sites from one version to another, this might be a good option.You just type www.example.com:81 in the browser window and you will be connected to the second apache instance.

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