Linux

Linux is a free Unix-type operating system originally created by Linus Torvalds with the assistance of developers around the world. Developed under the GNU General Public License , the source code for Linux is freely available to everyone.

Links

• linux kernel
• Distributions
• https://kb.novaordis.com/index.php/Events_OS_Metrics
• Linux on ircnet: #linux2

 

Rescue CDs

• Scientific Linux

• SystemRescueCd
• Knoppix

 

Checking resources

*inxi
*http://www.slashroot.in/linux-system-io-monitoring

show what is doing most disk accesses

*iotop 
glances

IO statistics

iostat
vmstat
dstat
ioping
atop

CPU usage etc

top
atop
htop
vtop
fio
pidstat

Administration

• About swap
• POSIX ACLS
• LVM
• Linux Software Raid
• Boot loader showdown: Getting to know LILO and GRUB

• Linux Power Management

 

FAQ

===Am i running in a hypervisor?

virt-what

check if interface exists

/sys/class/net/$IF

check if virtual or physical machine

dmidecode -s system-manufacturer
virt-who
lscpu

Find bios version

dmidecode -s bios-version

watch which files a process opens

watch ls -l /proc/`pidof clamd`/fd

Grow (GPT) last partition to max available

Where '3' is partition number

parted /dev/sdf resize 3 100%

No longer allowed?

gdisk

timestamp to human readable

date -d @1522142497

List hardware

• lshw
• dmidecode
• lsusb
• hwinfo
• lspci
• lscpu

dmidecode -t baseboard

BLKRRPART: Device or resource busy

spend all day or reboot

 

rescan partition table

Keep an eye on

cat /proc/partitions

Partition(s) have been written, but we have been unable to inform the kernel of the change

partprobe
kpartx /dev/sdg
partx -uv /dev/sdg (this one worked on centos 7.3!)

This one gave new disk size!

echo 1 > /sys/block/sde/device/rescan

Only one that seemed to work on (centos7.x)

echo "- - -" > /sys/class/scsi_host/host2/scan

or scan all:

echo "- - -" | tee /sys/class/scsi_host/host*/scan

The winner so far:

blockdev --rereadpt /dev/sdg

maybe

hdparm -z /dev/sdg

Force reboot

I found sometimes 'reboot' and 'shutdown' don't work in virtual machines, in that case try:

#sync
echo s > /proc/sysrq-trigger
#optionally umount
echo u > /proc/sysrq-trigger
#reboot
echo b > /proc/sysrq-trigger

Mignight commander/dialog strange characters

Quick fix:

export LANG=en_US.ISO-8859-1

This probleem seems to be related to screen/su -

kpartx failing silently

No output/result when trying to create:

kpartx -lv /dev/mapper/foo

this might means the device hasn't been partitioned

No output when trying to delete:

kpartx -d /dev/mapper/foop1

means you should use

kpartx -d /dev/mapper/foo

 

 

 

Create swapfile

fallocate -l 4G /var/swapfile
mkswap /var/swapfile

Temporary:

swapon -v /var/swapfile

In fstab: /var/swapfile swap swap sw,prio=-1

swapon failed: Invalid argument

problably trying to use fallocate on rhel/centos, use dd instead

partx: error adding partition

try kpartx instead