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.


*[[Gentoo]]
 
== Links ==
 
*[[Linux_kernel|linux kernel]]
*[[Distributions|Distributions]]
*https://kb.novaordis.com/index.php/Events_OS_Metrics
*Linux on ircnet: #linux2
 
 
== Rescue CDs ==
 
*[https://www.scientificlinux.org/downloads/ Scientific Linux]
 
*[[SystemRescueCd|SystemRescueCd]]
*[http://www.knoppix.net/ Knoppix]
 
 
 
== Checking resources ==
 
*inxi
*[http://www.slashroot.in/linux-system-io-monitoring http://www.slashroot.in/linux-system-io-monitoring]
 
===show what is doing most disk accesses===
 
*iotop
[https://github.com/nicolargo/glances glances]
 
=== IO statistics ===
 
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|LVM]]
*[[Linux_Software_Raid|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|Linux Power Management]]
 
 
 
 
 
 
== 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}'
  [[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}'