Procedure to mount ISO images under Linux
1) You must login as a root user
2) Create the directory i.e. mount point:
# mkdir -p /mnt/temp_disk1
3) Use mount command to mount iso file called disk1.iso with loop option:
# mount -o loop disk1.iso /mnt/temp_disk1
Now you should be able to access all the files on that ISO image. Please note, you have to provide full path to iso image, not just iso image alone.
Sometime ago installed my RedHat 5 with xen. Then I needed to create a virtual server running RedHat 4 in it, all needed to be 64 bit because Opsware required 64 bit RHEL AS4, so had to come up with an inexpensive solution. Got Intel Quad from Dell for $400 with 8gb ram, inexpensive desktop, installed RedHat 5 on it, then created xen virtual server in it running RedHat AS 4 for Opsware, of course opsware is not supported under XEN as a virtual server and it would not run under RedHat 5, so I had to hack it a bit to get it working, actually to get it installed is quite simple. Anyway so I had my RedHat AS4 vm running then I did notice that my desktop running all of that rebooted the other day, but my opsware virtual server did not start. With XEN I am not that familiar so I had issues starting it with command line, so I was ending up bringing xdisplay back to my pc remotely just to start it up. Well what it turned out that I don’t have to do this anymore. I was playing around with starting it up and why, I can do it automatically.
Anyway solution to start it up was very simple, on my RedHat 5 hyperviser I had to go to /etc/xen directory, there is directory called auto, and there is a config file for my virtual server called opsware (name of that virtual server) so to get it automatically started I needed to create a symbolic link inside that auto directory that pointed to that opsware config file.
Simple and easy, not when my desktop reboots my xen vm starts automatically. 
Just installed Red Hat AS4 and I am unable to login with root account. Passwd is all set but I am getting popup message saying “Root logins are not allowed”, simple solution is to press CTRL+ALT+F1 and switch to console login and you will be on your way Nice and simple.
This utility is so cool, how many times I did try to figure out netmasks, broadcasts etc, this utility actualy performs simple manipulation of IP addresses:
ipcalc – provides a simple way to calculate IP information for a host. The various options specify what information ipcalc should display on standard out. Multiple options may be specified. An IP address to operate on must always be specified. Most operations also require a netmask or a CIDR prefix as well.
# ipcalc -nbm 192.168.1.254/29
NETMASK=255.255.255.248
BROADCAST=192.168.1.255
NETWORK=192.168.1.248
#
I had server that rebooted and then was hanging at the GRUB line and was not booting, so I did decide to reinstall grub which seems like it did help. Here is the procedure that I did to get it boot again:
Reinstalling the Boot Loader
In many cases, the GRUB boot loader can mistakenly be deleted, corrupted, or replaced by other operating systems.
The following steps detail the process on how GRUB is reinstalled on the master boot record:
* Boot the system from an installation boot medium (CDROM or DVD)
* Type linux rescue at the installation boot prompt to enter the rescue environment.
* Type chroot /mnt/sysimage to mount the root partition.
* Type /sbin/grub-install /dev/sda to reinstall the GRUB boot loader, where /dev/sda is the boot partition.
* Review the /boot/grub/grub.conf file, as additional entries may be needed for GRUB to control additional operating systems.
* Reboot the system.
Done, system working again.
How to check what repository is your yum setup to retrieve packages from?
[root@server1 ~]# yum repolist
Loaded plugins: rhnplugin, security
repo id repo name status
rhel-i386-server-5 Red Hat Enterprise Linux (v. 5 for 32-bi enabled : 5,186
rhel-i386-server-clu RHEL Clustering (v. 5 for 32-bit x86) enabled : 116
rhel-i386-server-clu RHEL Cluster-Storage (v. 5 for 32-bit x8 enabled : 173
rhel-i386-server-vt- RHEL Virtualization (v. 5 for 32-bit x86 enabled : 148
rhn-tools-rhel-i386- Red Hat Network Tools for RHEL Server (v enabled : 385
repolist: 6,008
[root@server1 ~]#
[root@server2 ~]# yum repolist
Loaded plugins: rhnplugin, security
repo id repo name status
iRedMail Yum repo generated by iRedMail: i enabled : 54
rhel-x86_64-server-5 Red Hat Enterprise Linux (v. 5 for 64-bi enabled : 6,800
rpmforge Red Hat Enterprise 5Server – RPMforge.ne enabled : 8,163
repolist: 15,017
[root@server2 ~]#
How do I change my system timezone from the command line without using redhat-config-date?
In order to change the timezone of your system you will need to access the file /etc/sysconfig/clock directly:
#ZONE=”America/New_York”
ZONE=”GMT”
UTC=false
ARC=false
Note: If your system’s BIOS has UTC set to true, then set UTC to true. If it has it set to false, set it to false. UTC in the configuration file must always reflect your BIOS settings.
In order to get the particular zone you wish to use you must associate ZONE with a file located in /usr/share/zoneinfo. It is wise to note the directory structure because if you need to set the timezone to that of Shanghai which is located in the Asia directory you will then have to set your ZONE variable to the following :
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To mount /root/linux.iso file under /mnt directory.
issue the following commands.
# mount -o loop /root/linux.iso /mn/linux
to unmount
# umount /mnt/linux
for example:
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Physically connect HBA to disk array.
Create LUN on disk array (50 GB in this case).
Reboot server to see new LUN. Note 2 separate device files with same size. This is normal.
Reboot again and interrupt the boot process and enable BIOS on the HBA card by pressing Control-Q.
Find disk device names (select sdc and sde)
[root@chrysek log]# dmesg | grep sectors
SCSI device sda: 142577664 512-byte hdwr sectors (73000 MB)
SCSI device sda: 142577664 512-byte hdwr sectors (73000 MB)
SCSI device sdb: 1 512-byte hdwr sectors (0 MB)
SCSI device sdb: 1 512-byte hdwr sectors (0 MB)
SCSI device sdc: 104857600 512-byte hdwr sectors (53687 MB)
SCSI device sdc: 104857600 512-byte hdwr sectors (53687 MB)
SCSI device sdd: 1 512-byte hdwr sectors (0 MB)
SCSI device sdd: 1 512-byte hdwr sectors (0 MB)
SCSI device sde: 104857600 512-byte hdwr sectors (53687 MB)
SCSI device sde: 104857600 512-byte hdwr sectors (53687 MB)
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I have few dysks setup, local and on SAN, I needed to add additional 200gb partition to a system that is on SAN and I am not sure how to do it so that I would not mess this up. Here is what I have:
[root@hog8 etc]# df -k
Filesystem 1K-blocks Used Available Use% Mounted on
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