fedora 14 and intel graphic card : x11 won't start

Fatal server error
caught exception

Check your video driver:
lsmod | grep video

==> i915

Incase wanna see the card:
lspci

change the driver:
/etc/X11/xorg.conf

OR

system-config-display

(the GUI will work eventhough your X still not on)

>>>>>>>

choose VESA driver and if appear depth error message, just change the color depth to lower value.

>>>>>>>>

when u choose wrong driver, like NV (nvidia), it will give u error device not found, cause the card is not there.

multipath on linux - how the disk look like

modprobe -l | grep the "driver desc"

if not there, install it...
ex. go to brocade, download, install with some options like --update-initrd

after this the /sys/class/fc_host folder is there

after you scanning with
echo "1" > ............./issue_lip
echo "- - -" > ................../scan

the device will appear in proc/scsi/scsi file.

when you part it, you need to restart it:
ex. dm-2 will have dm-2p1 as partition 1, but you can not format it untill you reboot it, it will add another disk called dm-3 whcih is same with dm-2p1.

RHEL 4 does not have yum

You can either install it manually with some deps packages, or just use GUI :
system-config-application --isodir=/isoFolder

useful also when u have no CDRom

syslog in linux/redhat

File is in /etc/syslog.conf

by default:
*.info;mail.none;authrpiv.none;cron.none /var/log/messages


meaning logging all subject at info (and above) level but the mail and cron not.
to the messages file

To make it particular:
kern.=info (only kernel with level info)

Numerical Code Severity Reference
-------------- ------------------------------------------- ---------
0 Emergency: system is unusable [RFC3164]
1 Alert: action must be taken immediately [RFC3164]
2 Critical: critical conditions [RFC3164]
3 Error: error conditions [RFC3164]
4 Warning: warning conditions [RFC3164]
5 Notice: normal but significant condition [RFC3164]
6 Informational: informational messages [RFC3164]
7 Debug: debug-level messages [RFC3164]


7 is the most detail severity level.

Explanation free Command in Linux

total Used free shared buffers cached
Mem: 49415736 49139132 276604 0 5656 47368280
-/+ buffers/cache: 1765196 7650540
Swap: 5237180 20 5237160

Mem total : Mem used + free
Mem used : 49GB (ps + buffers 5656 + cache 47GB)


- buffer/cache : Mem used - (buffers 5656 + cache 47GB)
+ buffer/cache : Mem free + (buffers 5656 + cache 47GB)

Swap (paging/Hard disk) used is 20KB only.



Buffers and cache are considered low priority, they r using large mem when none uses it. when apps using it, they will be decreased.

Buffers is for remembering the FS like dir structure (ls -R . will boost the buffr)
cache is storing the file content, so processes can access file in cache instead read it over and over from the disk.

SCSI harddisk on linux

Manually:
cat /proc/scsi/scsi
ls /sys/class/scsi_host/.....
==> contain the host:bus:ID:Lun and Port name

By command:
lsscsi (many flag options)
fdisk -l
sginfo

Note : /dev/sdX mapped from /dev/sgX

When a HBA attach to SAN which contain 4 logical disks:
/dev/sdb,c,d,e (the partner is /dev/sdf,g,h,i)

How to see the partner :
e2label /dev/sdb XXX ==> to lable the HD
e2label /dev/sdf --> to see if it has same lable or not

Will be like this :
H:B:I:L == 5.0.0.1,2,3 (for sdb,c,d,e) and 5.0.1.1,2,3,4 (for the partner)

H is host, same as comes from one HBA. (diffrent from CDROM and LOCAL HD as it connects from different card)

B is BUS : dunno what
I is ID : same for LUNS (show same S/N of harddisk)
L is LUN : different for each partition/logical disks

additional commands:
hdparm
sdparm
scsi_id
parted /dev/sdX print ==> to see File System of a harddisk
rescan_scsi_bus.sh

Linux HD ATA problem : fsck, e2fsck

when disk has problem, normally you done fsck.

when fsck generates error like ext2 not recognized, please run e2fsck -b xxxx, this one what you must do:

1. linux rescue
2. fdisk /dev/sdX
3. fsck to each partition, NOT to the disk /dev/sda NOR to the swap NOR to the sda4(extended partition - 0 length partition)

If you got error about superblock, then:
4. each partition : mkfs -n -S /dev/sdXY
5. Get the superblock backup number xxxx, xxx, xxx and run : efsck -b xxxx /de/sdXY, try till succesfully

Reminder : Do not fsck to the disk /dev/sdX, but do it to the partition instead.