System Admin Q & A – VII

Ques 1: – What are the different modes in network bonding ?

Ans: – There are different modes in network bonding :
mode=0 (Balance-rr) – This mode provides load balancing and fault tolerance.
mode=1 (active-backup) – This mode provides fault tolerance.
mode=2 (balance-xor) – This mode provides load balancing and fault tolerance.
mode=3 (broadcast) – This mode provides fault tolerance.
mode=4 (802.3ad) – This mode provides load balancing and fault tolerance.
mode=5 (balance-tlb) – Prerequisite: Ethtool support in the base drivers for retrieving the speed of each slave.
mode=6 (Balance-alb) – Prerequisite: Ethtool support in the base drivers for retrieving the speed of each slave.

Ques 2: – What’s the difference between TCP &UDP ?

Ans: – TCP is a Transmission Control Protocol.
UDP is a User Datagram Protocol.
There are four major differences between UDP and TCP:
1. TCP can establishes a Connection and UDP cannot.
2. TCP provides a stream of unlimited length, UDP sends small packets.
3.TCP gurantees that as long as you have a connection data sent will arrive at the destination, UDP provides not guarantee delivery.
4.UDP is faster for sending small amounts of data since no connection setup is required, the data can be sent in less time then it takes for TCP to establish a connection.

Ques 3: – What are the fields of the password file?

Ans: – The /etc/passwd contains one entry per line for each user (or user account) of the system. All fields are separated by a colon (:) symbol. Total seven fields as follows.

An example record may be:

The fields, in order from left to right, are:

  1. The first field is the user name, i.e. the string a user would type in when logging into the operating system: the logname. Each record in the file must have a unique user name field.
  2. The second field stores information used to validate a user’s password; however in most modern uses this field is usually set to “x” (or some other indicator) with the actual password information being stored in a separate shadow password file. Setting this field to an asterisk “*” is the typical way to deactivate an account to prevent it being used.
  3. The third field is the user identifier, the number that the operating system uses for internal purposes. It does not have to be unique.
  4. The fourth field is the group identifier. This number identifies the primary group of the user; all files that are created by this user may initially be accessible to this group.
  5. The fifth field, called the Gecos field, is commentary that describes the person or account. Typically, this is a set of comma-separated values including the user’s full name and contact details.
  6. The sixth field is the path to the user’s home directory.

The seventh field is the program that is started every time the user logs into the system. For an interactive user, this is usually one of the system’s command line interpreters (shells).

Ques 4: – What is DDNS and why do I need it?

Ans: – Dynamic DNS (described in RFC 2136) allows servers to dynamically update and create records in DNS. Dynamic DNS is used by the Exchange server to create server records and other entries used by the Exchange Servers for things like message routing. In a simple Exchange organization, DDNS is not strictly necessary, but makes administration much easier.

Ques 5: – What do I need in order to install Exchange 2003?

Ans: – A partial list includes:
DNS (preferably DDNS)
Active Directory 2000 or 2003
Permissions to update the Schema
Hardware sufficient to run Exchange 2003

Windows 2000 SP3 applied to all DCs, GC, and all (future) E2K2 servers, or Windows 2003.

Ques 6: – What is POSIX? Name 2 POSIX-oriented operating systems?

Ans: – Portable Operating System Interface is the collective name of a family of related standards specified by the IEEE to define the application programming interface (API). HP-UX, Solaris, AIX etc

Ques 7: – When u try to create a file, u got a error that “No space available”. But actually space available on volume? How do u resolve this issue?

Ans: – Try this df -i list inode information instead of block usage [Perhaps are you out of inodes on this file system.], To “rectify it”, remove unwanted files or move them somewhere else.]

Ques 8: – whats is called 1.5 stage in boot process of linux?

Ans: – The 1.5 boot loader is stored (if needed) in the MBR or the boot partition.The great thing about GRUB is that it includes knowledge of Linux file systems. Instead of using raw sectors on the disk, as LILO does, GRUB can load a Linux kernel from an ext2 or ext3 file system. It does this by making the two-stage boot loader into a three-stage boot loader.

Stage 1 (MBR) boots a stage 1.5 boot loader that understands the particular file system containing the Linux kernel image.Examples include reiserfs_stage1_5(to load from a Reiser journaling file system) or e2fs_stage1_5(to load from an ext2 or ext3 file system). When the stage 1.5 boot loader is loaded and running, the stage 2 boot loader can be loaded.”

So Basically,

Stage 1 Boot loader is MBR
Stage 2 Boot loader is GRUB
Stage 1.5 Boot loader is e2fs_stage1_5

(Basically this module will load the knowledge of Filesystem to Grub to read the kernel)

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