How to open ports in Red Hat Linux

1. Edit vi /etc/sysconfig/iptables
2. Add -A RH -INPUT -m state --state NEW -m tcp -p tcp --dport port number -j ACCEPT
Change 'port number' to desired port number
3. save and exit
4. restart iptables with 'service iptables restart'

when we mounting chroot /mnt/sysimage we are getting below error, chroot: cannot run command '/bin/sh' :No such file or directory

# ls /bin/sh 

If the command returns no file or directory again, then run

# ls /bin/bash

If this command returns the path of /bin/bash then recreate the symlink from /bin/sh to /bin/bash as such:

# ln -s /bin/sh /bin/bash

Why do I get this error '/dev/st0: inappropriate ioctl for device'

When I run the command mt -f /dev/st0 status, it produces /dev/st0:inappropriate ioctl for device. How do I fix this issue?

How do I open doc files from command line in linux

Doc files can be opened following default tools.

1. gnome-open
2. oowriter
3. xdg-open


For example:

#gnome-open test.doc
#oowriter test1.doc
#xdg-open test2.doc

How to measure linux performance

Check with dd command in unix/linux systems... for example

#time dd if=/dev/zero of=/dev/null bs=1024k count=10000000
10000000+0 records in
10000000+0 records out
10485760000000 bytes (10 TB) copied, 359.587 seconds, 29.2 GB/s

real    5m59.615s
user    0m4.403s
sys     5m54.958s

#top
#ps

CIFS VFS: cifs_mount failed w/return code = -101

CIFS VFS: Error connecting to socket. Aborting operation
 CIFS VFS: cifs_mount failed w/return code = -101