Difference between revisions of "Linux"

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Linux is a free Unix-type operating system originally created by [http://en.wikipedia.org/wiki/Linus_Torvalds Linus Torvalds] with the assistance of developers around the world. Developed under the [http://www.linux.org/info/gnu.html GNU General Public License] , the source code for Linux is freely available to everyone.
Linux is a free Unix-type operating system originally created by [http://en.wikipedia.org/wiki/Linus_Torvalds Linus Torvalds] with the assistance of developers around the world. Developed under the [http://www.linux.org/info/gnu.html GNU General Public License] , the source code for Linux is freely available to everyone.


== Links ==
== Links ==
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*[[Linux_kernel|linux kernel]]  
*[[Linux_kernel|linux kernel]]  
*[[Distributions|Distributions]]  
*[[Distributions|Distributions]]  
 
*https://kb.novaordis.com/index.php/Events_OS_Metrics
*Linux on ircnet: #linux2
 
 


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


=== show what is doing most disk accesses ===
===show what is doing most disk accesses===


  iotop  
  *iotop  
  glances
  [https://github.com/nicolargo/glances glances]


=== IO statistics ===
=== IO statistics ===
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== FAQ ==
== FAQ ==


=== check if virtual of physicalmachine ===
=== check if interface exists ===
 
/sys/class/net/$IF
 
===check if virtual or physical machine===


  dmidecode -s system-manufacturer
  dmidecode -s system-manufacturer
  virt-who
  virt-who
lscpu
virt-what


 
===Find bios version===
dmidecode -s bios-version
 
=== watch which files a process opens ===
 
watch ls -l /proc/`pidof clamd`/fd


=== pam_succeed_if(sudo:auth): requirement "uid >= 1000" not met ===
=== pam_succeed_if(sudo:auth): requirement "uid >= 1000" not met ===
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*lsusb  
*lsusb  
*hwinfo  
*hwinfo  
*lspci  
*lspci
*lscpu


  dmidecode -t baseboard
  dmidecode -t baseboard
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=== calling ioclt to re-read partition table: Device or resource busy ===
=== calling ioclt to re-read partition table: Device or resource busy ===


=== rescan partition table ===
=== rescan partition table ===
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  partprobe
  partprobe
  kpartx /dev/sdg
  kpartx /dev/sdg
  partx -uv /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
  echo 1 > /sys/block/sde/device/rescan


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  echo "- - -" > /sys/class/scsi_host/host2/scan
  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
  blockdev --rereadpt /dev/sdg
but may throw blockdev: ioctl error on BLKRRPART: Device or resource busy


maybe
maybe
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=== Create swapfile ===
=== Create swapfile ===
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  fallocate -l 4G /var/swapfile
  fallocate -l 4G /var/swapfile
  mkswap /var/swapfile
  mkswap /var/swapfile
Temporary:
  swapon -v /var/swapfile
  swapon -v /var/swapfile
In fstab: /var/swapfile swap swap sw,prio=-1


swapon failed: Invalid argument
swapon failed: Invalid argument
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=== partx: error adding partition ===
=== partx: error adding partition ===
try kpartx instead
try kpartx instead




===Find maximum depth of directory===
find /var/www -type d | awk -F"/" 'NF > max {max = NF} END {print max}'
   [[Category:System Administration]] [[Category:Linux]]
   [[Category:System Administration]] [[Category:Linux]]

Latest revision as of 14:17, 11 July 2022

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

 

Rescue CDs

 

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

 



FAQ

check if interface exists

/sys/class/net/$IF

check if virtual or physical machine

dmidecode -s system-manufacturer
virt-who
lscpu
virt-what

Find bios version

dmidecode -s bios-version

watch which files a process opens

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

pam_succeed_if(sudo:auth): requirement "uid >= 1000" not met

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

 

calling ioclt to re-read partition table: Device or resource busy

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

but may throw blockdev: ioctl error on BLKRRPART: Device or resource busy


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


Find maximum depth of directory

find /var/www -type d | awk -F"/" 'NF > max {max = NF} END {print max}'