Linux: Difference between revisions

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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 ==
*[[linux kernel]]
*[[Distributions]]


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


== Rescue CDs ==
== Rescue CDs ==
*[https://www.scientificlinux.org/downloads/ Scientific Linux]


*[[SystemRescueCd]]
*[https://www.scientificlinux.org/downloads/ Scientific Linux]
*[http://www.knoppix.net/ Knoppix]
 
*[[SystemRescueCd|SystemRescueCd]]  
*[http://www.knoppix.net/ Knoppix]  
 
 
 


== Administration ==


==Checking resources==
*[https://chrisdown.name/2018/01/02/in-defence-of-swap.html About swap]
*inxi
*[http://www.suse.de/~agruen/acl/linux-acls/online/ POSIX ACLS]
*http://www.slashroot.in/linux-system-io-monitoring
*[[LVM|LVM]]
===show what is doing most disk accesses===
*[[Linux_Software_Raid|Linux Software Raid]]
iotop
*[http://www-128.ibm.com/developerworks/library/l-bootload.html Boot loader showdown: Getting to know LILO and GRUB]
glances


===IO statistics===
*[[Linux_Power_Management|Linux Power Management]]
iostat
vmstat
dstat
ioping
atop


===CPU usage etc===
 
top
atop
htop
vtop
fio
pidstat


==Administration==
*[https://chrisdown.name/2018/01/02/in-defence-of-swap.html About swap]
*[http://www.suse.de/~agruen/acl/linux-acls/online/ POSIX ACLS]
*[[LVM]]
*[[Linux Software Raid]]
*[http://www-128.ibm.com/developerworks/library/l-bootload.html Boot loader showdown: Getting to know LILO and GRUB]


*[[Linux Power Management]]


==FAQ==
===check if virtual of physicalmachine===
dmidecode -s system-manufacturer
virt-who


= FAQ =
==Storage==
===Umount: /mnt/sda1 is busy===
Try
umount -lf /mnt/sda1


=== Grow (GPT) last partition to max available ===


===pam_succeed_if(sudo:auth): requirement "uid >= 1000" not met===
===Grow (GPT) last partition to max available===
Where '3' is partition number
Where '3' is partition number
  parted /dev/sdf resize 3 100%
  parted /dev/sdf resize 3 100%
No longer allowed?
No longer allowed?


  gdisk
  gdisk


===timestamp to human readable===
===I deleted a file but disk is still full===
  date -d @1522142497
It was in use by process, you'll need to kill that
===List hardware===
lsof -nP | grep '(deleted)'
*lshw
etc
*dmidecode
 
*lsusb
==Network==
*hwinfo
 
=== check if interface exists ===
 
/sys/class/net/$IF
 
 
==Hardware info==
===Check number of CPUs===
lscpu | grep Socket
 
===Find bios version===
  dmidecode -s bios-version
 
 
=== pam_succeed_if(sudo:auth): requirement "uid >= 1000" not met ===
 
 
 
 
 
=== List hardware ===
 
*lshw  
*dmidecode  
*lsusb  
*hwinfo  
*lspci
*lspci
*lscpu


  dmidecode -t baseboard
  dmidecode -t baseboard


===rescan partition table===
=== 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
  partprobe
  kpartx
  kpartx /dev/sdg
partx -uv /dev/sdg (this one worked on centos 7.3!)
 
This one gave new disk size!
Verified: CentOS 6, Ubuntu 22
  echo 1 > /sys/block/sde/device/rescan
  echo 1 > /sys/block/sde/device/rescan
  echo "- - -" > /sys/class/scsi_host/host2/scan


===Force reboot===
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:
I found sometimes 'reboot' and 'shutdown' don't work in virtual machines, in that case try:
  #sync
  #sync
  echo s > /proc/sysrq-trigger
  echo s > /proc/sysrq-trigger
Line 86: Line 141:
  echo b > /proc/sysrq-trigger
  echo b > /proc/sysrq-trigger


===Mignight commander/dialog strange characters===
==Misc==
 
===check if you're in virtual or physical machine===
 
dmidecode -s system-manufacturer
virt-who
lscpu
virt-what
 
=== watch which files a process opens ===
 
watch ls -l /proc/`pidof clamd`/fd
 
=== timestamp to human readable ===
 
date -d @1522142497
 
=== Mignight commander/dialog strange characters ===
 
Quick fix:
Quick fix:
  export LANG=en_US.ISO-8859-1
  export LANG=en_US.ISO-8859-1


This probleem seems to be related to screen/su -
This probleem seems to be related to screen/su -


[[Category: System Administration]]
=== kpartx failing silently ===
[[Category: Linux]]
 
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}'
  [[Category:System Administration]] [[Category:Linux]]
 
 
===pvcreate: Cannot use /dev/sdb: device is partitioned===
Even /proc/partitions will confirm there's no partitions, so to convince pvcreate:
wipefs --all /dev/sdb

Latest revision as of 11:04, 15 November 2023

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

 


Administration

 



FAQ

Storage

Umount: /mnt/sda1 is busy

Try

umount -lf /mnt/sda1

Grow (GPT) last partition to max available

Where '3' is partition number

parted /dev/sdf resize 3 100%

No longer allowed?

gdisk

I deleted a file but disk is still full

It was in use by process, you'll need to kill that

lsof -nP | grep '(deleted)'

etc

Network

check if interface exists

/sys/class/net/$IF


Hardware info

Check number of CPUs

lscpu | grep Socket

Find bios version

dmidecode -s bios-version


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

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! Verified: CentOS 6, Ubuntu 22

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

Misc

check if you're in virtual or physical machine

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

watch which files a process opens

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

timestamp to human readable

date -d @1522142497

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}'


pvcreate: Cannot use /dev/sdb: device is partitioned

Even /proc/partitions will confirm there's no partitions, so to convince pvcreate:

wipefs --all /dev/sdb