Archive for August, 2008

user nobody

There is some default user at Linux/Unix system. nobody is one of them. It has no login shell. That means this user can never login at the system. The user id of the nobody user is 99. and the group id is 99.

The nobody account is suppose to be used for anonymous NFS access.

From a Solaris viewpoint:
nobody — Assigned to users or software processes that do not need nor should have any special permissions. nobody is used in patch installation process, NFS, Web servers and directory services. This is an anonymous user account, assigned by an NFS server when a request is received from an unauthorized root user. NFS uses it to secure file servers on networks where diskless clients can be rebooted in single-user mode by anyone with physical access. The nobody user account is also assigned to software processes that do not need nor should have any special permissions. Some daemons, such as fingerd, run as nobody. If in.tftpd is enabled, it will run as the user nobody. Disabling this account will interfere with patching your system, NFS services as will as causing problems in other areas.

noaccess — The account that is assigned to a user or a process that needs access to a system through some application but without actually logging in.

nobody4 — SunOS 4.0 or 4.1 version of the nobody user account. The nobody4 user can actually be eliminated if you’re absolutely certain you’ll never need to use/access SunOS 4.x services. Disabling this account would interfere with communications between earlier revisions on SunOS (4.x).

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in linux, one pc restart momentarily

Today I get a problem “suppose in linux, one pc restart momentarily.then how do u solved it?”

My suggestion regarding this issue is as follows,

it may occur because of many issue.
1. may be hardware problem.
2. may be OS problem
3. may be configuration problem of inittab file.

If the problem is with hardware then you have to fix the hardware.
If the problem is with the OS then install a fresh OS.

If you boot your OS at run level 6 then the pc will restart momentarily. You have to change the default run level. As your pc is also restarting momenterily, you must have to log in at single user mode to change the configuration at /etc/inittab .

In my next post I shall try to discuss to change the default run-level.

Any comments regarding these issue will be highly welcome.

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Generic Host Process for Win32 has encountered a problem and needs to close.

Today I got a mail with a following problem.

I am getting this error which says “Generic Host Process for Win32 has encountered a problem and needs to close. We are sorry for inconvenience.”
After getting this error, computer acts rather scary! Internet is disconnected (BroadBand) and wont allow me to connect again until I restart my computer.

Normally this problem occurs due to installing two Antivirus at the same pc. After uninstalling one the problem gets solved.

Sometimes anti-virus and spy-ware (both are installed) cause this problem. After uninstalling one, the problem gets solved.

This occured because, Two Anti-Virus and two Anti-Spyware programs monitoring your system at the same time.

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why runlevel-4 didn’t use?

Today I have got this comment from one of my friend. One thing I want to clear you that, run levels are not same for all linux version. Suppose here is usage of run level 4 at different versions:
Redhat/Fedora          Normally not used (user definable).

SUSE                        Normally not used (user definable).

Slackware                 Full multi-user with display manager

Gentoo Linux            Aliased for runlevel 3 (Full multi-user with display manager)

System V                  Multi-user, user-defined

Solaris                     Alternative multi-user, user-defined

HP-UX                     Multi-user with VUE started instead of CDE

In fine we may say that in maximum cases run level 4 is user defined. Runlevel 4 is usually a “custom” level. By default it will start a few more services than level 3. This level is usually only used under special circumstances.

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Clonning a MAC address of NIC at linux

To clone a MAC address of a NIC at Linux we can use the following commands.

1. We have to get down the interface in which we are going to clone. Here we are clonning on interface eth0.

#ifdown eth0

2. Now we will add the MAC address at the interface eth0 with the following command.

#ifconfig eth0 hw ether 00:05:5B:33:A3:15

3. Now bring the interface up.

#ifup eth0

If we want to use the MAC permanently we can add the three command at /etc/rc.local file .

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Runlevel at linux

There are 7 runlevels at linux. these are:

runlevel 0 –> shutdown

runlevel 1–> single user

runlevel 2–> multiuser without NFS

runlevel 3–> multiuser with NFS

runlevel 4–> normally not in use (User defined)

runlevel 5 –> Graphical user interface

runlevel 6 –> restart

We can go to any runlevel by typing init runlevel . As for example to go to graphical user mode we can type init 5. To restart we can type init 6, to shutdown init 0 etc.

The run level differs according to the OS. Suppose HP-UX, Solaris, Redhat, SUSE, Debian—– have different run level system. Redhat, SUSE, Debian are same. Others are a little different.

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Some Commands to shutdown and restart Linux OS

To shutdown we can use any of the following commands.

#init 0

#poweroff

#shutdown -h now

#shutdown -h 0

#shutdown -h 10 (will shutdown after 10 minutes)

#halt -p

To restart we can use any of the following commands:

#init 6

#reboot

#shutdown -h now

Ctrl+Alt+Delete (3 finger salute)

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