Linux Tipps und Tricks
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...
# echo 1 > /proc/sys/kernel/sysrq
# echo b > /proc/sysrq-trigger
First line enables sysrq, second line sends the reboot request.
For more look at kernel.org!
Scan all SCSI buses for new devices
# for i in /sys/class/scsi_host/host*/scan ; do echo "- - -" > $i ; done
Rescan a device (for example after changing a VMDK size)
# echo 1 > /sys/class/block/${device}/device/rescan
This is for device sda after changing the VMDK from 20GB to 25GB:
# device=sda
# echo $[ 512 * $(cat /sys/block/${device}/size) / 1024 / 1024 / 1024 ]
20
# echo 1 > /sys/class/block/${device}/device/rescan
# echo $[ 512 * $(cat /sys/block/${device}/size) / 1024 / 1024 / 1024 ]
25
# parted /dev/${device} print free
Warning: Not all of the space available to /dev/sda appears to be used, you can fix the GPT to use all of the space (an extra 10485760 blocks) or
continue with the current setting?
Fix/Ignore? F
Model: VMware Virtual disk (scsi)
Disk /dev/sda: 26,8GB
Sector size (logical/physical): 512B/512B
Partition Table: gpt
Disk Flags:
Number Start End Size File system Name Flags
2 17,4kB 1049kB 1031kB bios_grub
1 1049kB 21,5GB 21,5GB zfs
21,5GB 26,8GB 5369MB Free Space
I want to put the free space into partition 1 and resize the rpool:
# parted /dev/${device} "resizepart 1 -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 -
# zpool set autoexpand=on rpool
# zpool online rpool sda1
# 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 -
# zpool set autoexpand=off rpool
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:
# 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
Then check it is not longer in use:
- mount
- pvs
- zpool status
- etc.
Then delete it:
# echo 1 > /sys/bus/scsi/drivers/sd/32\:0\:0\:0/delete
The 32:0:0:0 is the number reported from the lsscsi above.
Et voila:
# 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
Copy a GPT partition table
Copy partition table of sdX to sdY:
# sgdisk /dev/sdX --replicate=/dev/sdY
# sgdisk --randomize-guids /dev/sdY
-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
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
Resize the partition
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.
Optional: Resize the ZPool in it
Check the actual values:
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
Now inform ZPool to grow to the end of the partition. Set autoexpand to on:
root@mariadb:~# zpool set autoexpand=on MYSQL-DATA
Send an online to the already onlined device to force a recheck in the ZPool to resize it without export/import:
root@mariadb:~# zpool online MYSQL-DATA /dev/sdb1
Et voila:
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 -
Set autoexpand to off if you want prevent to autoexpand if partition grows:
root@mariadb:~# zpool set autoexpand=off MYSQL-DATA
