Linux Tipps und Tricks

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Revision as of 16:21, 25 November 2021 by Lollypop (talk | contribs) (Text replacement - "<source" to "<syntaxhighlight")
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Hard reboot

This is the hard way to kick your kernel into void. No filesystem sync is done, just and ugly fast direkt reboot! You should never do this... <syntaxhighlight lang=bash>

  1. echo 1 > /proc/sys/kernel/sysrq
  2. echo b > /proc/sysrq-trigger

</source> First line enables sysrq, second line sends the reboot request.

For more look at kernel.org!

Scan all SCSI buses for new devices

<syntaxhighlight lang=bash>

  1. for i in /sys/class/scsi_host/host*/scan ; do echo "- - -" > $i ; done

</source>

Scan all FC ports for new devices

!!!Be CAREFUL!!! This command line issues a Loop Initialization Protocol (LIP). This is a bus reset hat means that removed devices in the fabric will disappear and new ones will appear. !!!BUT the connection might get lost for a moment!!! The softer way is to scan the SCSI buses. <syntaxhighlight lang=bash>

  1. for i in /sys/class/fc_host/*/issue_lip ; do echo "1" > $i ; done

</source>

Rescan a device (for example after changing a VMDK size)

<syntaxhighlight lang=bash>

  1. device=sda
  2. echo 1 > /sys/class/block/${device}/device/rescan

</source>

This is for device sda after changing the VMDK from 20GB to 25GB: <syntaxhighlight lang=bash>

  1. device=sda
  2. echo $[ 512 * $(cat /sys/block/${device}/size) / 1024 ** 3 ]

20

  1. echo 1 > /sys/class/block/${device}/device/rescan
  2. echo $[ 512 * $(cat /sys/block/${device}/size) / 1024 ** 3 ]

25

  1. parted /dev/${device} "print free"

Warning: Not all of the space available to /dev/sda appears to be used, you can fix the GPT to use all of the space (an extra 10485760 blocks) or continue with the current setting? Fix/Ignore? F Model: VMware Virtual disk (scsi) Disk /dev/sda: 26,8GB Sector size (logical/physical): 512B/512B Partition Table: gpt Disk Flags:

Number Start End Size File system Name Flags 

2      17,4kB  1049kB  1031kB                     bios_grub
1      1049kB  21,5GB  21,5GB  zfs
       21,5GB  26,8GB  5369MB  Free Space

</source>

I want to put the free space into partition 1 and resize the rpool: <syntaxhighlight lang=bash>

  1. parted /dev/${device} "resizepart 1 -1"
  2. parted /dev/${device} "print free"

Model: VMware Virtual disk (scsi) Disk /dev/sda: 26,8GB Sector size (logical/physical): 512B/512B Partition Table: gpt Disk Flags:

Number Start End Size File system Name Flags 

2      17,4kB  1049kB  1031kB                     bios_grub
1      1049kB  26,8GB  26,8GB  zfs
       26,8GB  26,8GB  983kB   Free Space
  1. zpool list rpool

NAME SIZE ALLOC FREE EXPANDSZ FRAG CAP DEDUP HEALTH ALTROOT rpool 19,9G 1,68G 18,2G - 14% 8% 1.00x ONLINE -

  1. zpool set autoexpand=on rpool
  2. zpool status rpool
 pool: rpool
state: ONLINE
 scan: none requested

config:

NAME STATE READ WRITE CKSUM rpool ONLINE 0 0 0 sda1 ONLINE 0 0 0

  1. zpool online rpool sda1
  2. zpool list rpool

NAME SIZE ALLOC FREE EXPANDSZ FRAG CAP DEDUP HEALTH ALTROOT rpool 24,9G 1,69G 23,2G - 11% 6% 1.00x ONLINE -

  1. zpool set autoexpand=off rpool

</source> Done.

Remove a SCSI-device

Let us say we want to remove /dev/sdb.

Be careful! Like in this example the lowest SCSI-ID is not always the lowest device name! Check it with lsscsi from the Ubuntu package lsscsi: <syntaxhighlight lang=bash>

  1. lsscsi

[2:0:0:0] cd/dvd NECVMWar VMware SATA CD00 1.00 /dev/sr0 [32:0:0:0] disk VMware Virtual disk 1.0 /dev/sdb [32:0:1:0] disk VMware Virtual disk 1.0 /dev/sda </source>

Then check it is not longer in use:

  1. mount
  2. pvs
  3. zpool status
  4. etc.

Then delete it: <syntaxhighlight lang=bash>

  1. echo 1 > /sys/bus/scsi/drivers/sd/32\:0\:0\:0/delete

</source> The 32:0:0:0 is the number reported from the lsscsi above.

Et voila: <syntaxhighlight lang=bash>

  1. lsscsi

[2:0:0:0] cd/dvd NECVMWar VMware SATA CD00 1.00 /dev/sr0 [32:0:1:0] disk VMware Virtual disk 1.0 /dev/sda </source>

Copy a GPT partition table

Copy partition table of sdX to sdY: <syntaxhighlight lang=bash>

  1. sgdisk /dev/sdX --replicate=/dev/sdY
  2. sgdisk --randomize-guids /dev/sdY

</source>

Or with: <syntaxhighlight lang=bash>

  1. sgdisk --backup=sdX.table /dev/sdX
  2. sgdisk --load-backup=sdX.table /dev/sdY
  3. sgdisk -G /dev/sdY

</source> 

       -R, --replicate=second_device_filename
              Replicate  the  main device's partition table on the specified second device.  Note that the replicated partition table is an exact
              copy, including all GUIDs; if the device should have its own unique GUIDs, you should use the -G option on the new disk.

       -G, --randomize-guids
              Randomize the disk's GUID and all partitions' unique GUIDs (but not their partition type code GUIDs). This  function  may  be  used
              after cloning a disk in order to render all GUIDs once again unique.

Resize a GPT partition

The partition was resized in VMWare from ~6GB to ~50GB.

In the VM I did Remove a SCSI-device for the resized device and then Scan all SCSI buses for new devices after that parted saw the new size.

Correct the GPT partition table

<syntaxhighlight lang=bash> root@mariadb:~# parted /dev/sdb GNU Parted 3.2 Using /dev/sdb Welcome to GNU Parted! Type 'help' to view a list of commands. (parted) p Warning: Not all of the space available to /dev/sdb appears to be used, you can fix the GPT to use all of the space (an extra 92274688 blocks) or continue with the current setting? Fix/Ignore? F <-- ! choose F Model: VMware Virtual disk (scsi) Disk /dev/sdb: 53,7GB <-- ! the new size is reported now Sector size (logical/physical): 512B/512B Partition Table: gpt Disk Flags:

Number Start End Size File system Name Flags 

1      1049kB  6442MB  6441MB  zfs

</source>

Resize the partition

<syntaxhighlight lang=bash> root@mariadb:~# parted /dev/sdb GNU Parted 3.2 Using /dev/sdb Welcome to GNU Parted! Type 'help' to view a list of commands. (parted) p Model: VMware Virtual disk (scsi) Disk /dev/sdb: 53,7GB Sector size (logical/physical): 512B/512B Partition Table: gpt Disk Flags:

Number Start End Size File system Name Flags 

1      1049kB  6442MB  6441MB  zfs

(parted) resizepart 1 End? [6442MB]? 53,7GB <-- ! Put new size here (parted) p <-- ! Control if it worked Model: VMware Virtual disk (scsi) Disk /dev/sdb: 53,7GB Sector size (logical/physical): 512B/512B Partition Table: gpt Disk Flags:

Number Start End Size File system Name Flags 

1      1049kB  53,7GB  53,7GB  zfs

(parted) q Information: You may need to update /etc/fstab. </source>

Optional: Resize the ZPool in it

Check the actual values: <syntaxhighlight lang=bash> root@mariadb:~# zpool list MYSQL-DATA NAME SIZE ALLOC FREE EXPANDSZ FRAG CAP DEDUP HEALTH ALTROOT MYSQL-DATA 5,97G 994M 5,00G 44G 47% 16% 1.00x ONLINE - root@mariadb:~# zpool get autoexpand MYSQL-DATA NAME PROPERTY VALUE SOURCE MYSQL-DATA autoexpand off default </source>

Now inform ZPool to grow to the end of the partition. Set autoexpand to on: <syntaxhighlight lang=bash> root@mariadb:~# zpool set autoexpand=on MYSQL-DATA </source>

Send an online to the already onlined device to force a recheck in the ZPool to resize it without export/import: <syntaxhighlight lang=bash> root@mariadb:~# zpool online MYSQL-DATA /dev/sdb1 </source>

Et voila: <syntaxhighlight lang=bash> root@mariadb:~# zpool list MYSQL-DATA NAME SIZE ALLOC FREE EXPANDSZ FRAG CAP DEDUP HEALTH ALTROOT MYSQL-DATA 50,0G 994M 49,0G - 5% 1% 1.00x ONLINE - rpool 19,9G 3,36G 16,5G - 19% 16% 1.00x ONLINE - </source>

Set autoexpand to off if you want prevent to autoexpand if partition grows: <syntaxhighlight lang=bash> root@mariadb:~# zpool set autoexpand=off MYSQL-DATA </source>

Optional: Resize the LVM physical volume

Check the values: <syntaxhighlight lang=bash>

  1. parted /dev/${device} "print free"

Model: VMware Virtual disk (scsi) Disk /dev/sda: 48.3GB Sector size (logical/physical): 512B/512B Partition Table: msdos Disk Flags:

Number Start End Size Type File system Flags 

       32.3kB  1049kB  1016kB           Free Space
1      1049kB  48.3GB  48.3GB  primary               boot
       48.3GB  48.3GB  999kB            Free Space
  1. pvs
 PV         VG      Fmt  Attr PSize   PFree
 /dev/sda1  vg-root lvm2 a--  <35.00g    0

</source> OK, we need to resize the physical volume <syntaxhighlight lang=bash>

  1. pvresize /dev/sda1
 Physical volume "/dev/sda1" changed
 1 physical volume(s) resized / 0 physical volume(s) not resized

</source> Check the values: <syntaxhighlight lang=bash>

  1. pvs
 PV         VG      Fmt  Attr PSize   PFree 
 /dev/sda1  vg-root lvm2 a--  <45.00g 10.00g

</source> Done.

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