I can only comment from my experience, which is primarily ext2 and ext3. > 1) How file systeem get corrupted on linux? I've almost never seen corruption in a Linux file system, the primary reason is usually a hardware issue, the secondary reason (by far) is buggy code. > 2) why,when and how fsck to be run without lossing data? fsck can never guarantee data will not be lost, it does the best it can, which is usually pretty good. Normally fsck is run in "single user mode". If you want to run it manually, you'd bring the system to single user mode (init 1) or it would run automatically during boot. There is a counter in the file system as to the last time fsck was run, during boot if this exceeds a certain vaule, fsck is run. There is also a clean shutdown bit which is set during a normal shutdown/dismount, if this is not se,t which indicates a possible system crash, fsck is run during system boot. > 4) what are all the precaution to be made to prevent file system > corruption. Run a "production" distribution such as Redhat/CentOS vs. more of a bleeding edge distribution such as Fedora. More than this, assume there will be data loss or corruption at some point and take precautions such as running RAID 1, backups and use a UPS to avoid system crashes or hardware issues in the face of brown or black outs. Lastly choose a journaling file system such as ext3, use ext2 for partitions were performance over consistency is more important. > 5) why & when the system will get hanged and what are all the possible > reasons? Usually hardware issues, particularly memory and hard drives. Most distributions come with memtest86 so that the hardware's memory can be thoroughly tested prior to installation of the operating system. Brett