Month: October 2021

iMac 27″ Video Card Repair Using Heat Gun

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iMac 27" Video Card Repair Using Heat Gun

Refering to some YouTube video, I tried to repair my iMac 27" (Mid 2011) Video Card, because my iMac could not boot and only apple logo appears. Steps as below

Hardware Info

Information
Identifier iMac12,2
Model A1312 (EMC 2429)
Family iMac (27-inch, Mid 2011)
CPU 3.4 GHz Intel Core i7
Graphic AMD Radeon HD 6970M 2048 MB

Steps

Take out glass panel

Use sucker to take it out.

Take out screen

Got 8 screws.

Take out power supply

Power Supply Cable Connectors

Power Supply Screws

Left of Power Supply

Take out CDROM Drive

CD Drive

CD Temperature Sensor

Take out fan

Fan

Fan (no screw)

Take out main board

Mainboard Battery

Mainboard Screws

Mainboard Below Fan

Below Fan

Below Fan Cables

Bottom

Infra-ray

Mainboard Wifi

Speaker

Speaker Cable

Speaker Connection

Just for info

Battery

Take out main board back cable

Mainboard Back

Mainboard Back Unplug

Take out video card

Video Fan

Right Top Video Card

GPU

GPU Back

GPU Heat Sink

GPU Heat Sink Screws

GPU Screws

GPU no Screw

Damages

The video card to LCD screen cable damaged, bought new one, waiting for delivery.

Damaged Cable

LCD Cable

Working now

Oct 13, After purchased cable, replace it, works immeditially, then continue OS reinstallation.

Future use

Due to this machine is too hot, I think better only use it in aircon room, and no background service should be executed.

References

My iMac is different model as below, but similar.

A1312 iMac GPU Replacement
Late 2009 iMac 27" Video Card Repair — 4850 — 2nd Bake

Rsync Basic

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Rsync Basic

rsync a directory to a new directory with different name

A trailing slash on the source avoids creating an additional directory level at the destination.

rsync -a src/ dest

You can think of a trailing / on a source as meaning "copy the contents of this directory" as opposed to "copy the directory by name".

Show progress

rsync -a -P src dest
rsync -a --progress src dest

Location of core files in Linux

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Location of core files in Linux

Some core files are in the executable file running directory, some core files are in system directory, depending on the system configuration.

Filename

By default, the core file name is core only, different OSs change it's name.

Software

Abrt

Abrt stores core files in /var/cache/abrt.

Apport

Apport stores core files in /var/crash.

Systemd

Systemd updated /proc/sys/kernel/core_pattern as below.

$ cat /proc/sys/kernel/core_pattern
|/usr/lib/systemd/systemd-coredump %p %u %g %s %t %e

OS

TrueNAS Scale

The core files in Linux can be found in /var/db/system/cores/, they can be removed if no debugging required.

Fedora

Fedora store core files in /var/spool/abrt/ instead

Archlinux

Archlinux stores core files in /var/lib/systemd/coredump/

Create timemachine share in TrueNAS

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Create timemachine share in TrueNAS

Note: I got issue suddenly after sometimes, and spent hours to fix it. End up, I switched back to Synology NAS as timemachine. Check Update section.

Tried many hours on setting up time machine backup in TrueNAS Scale, encountered many issues. To save time next time, record important steps and parameters for for next setup.

Create dataset

Create a dataset called timemachine under zpool pool1. Set ACL Type of dataset to POSIX.

Create user

Creating new user/group is not a good way if the NAS is also used for other user from same machine at same time. This is because the TrueNAS will use both user to login, which is hard to troubleshoot and confusing. If do not create new user, the ownership/permission of sharing dataset is also hard to decide. To use dedicated user for timemachine, following steps can be used.

Create a new named as user id tm with group tm. It will create a sub-dataset in ZFS under timemachine dataset. Change home directory of tm to the dataset created in Create dataset section.

The Auxiliary Groups have a group named as builtin_users. Beware of this group, it will appear later in this post again.

Note: If the backup folder was copied from other system, change the owner/group to tm:builtin_users, and permission to 775 to avoid permssion issue.

Set permission of dataset

Strip ACL

This is most easy way with lesser headache. Remove ACL if ACL is wong or just use traditional UNIX permission system.

Use ACL

Change owner and group to both tm.

The dataset permission set to POSIX_HOME, this will enable owner and group both have read/write/execute permission, others will be read only.

Create share

In TrueNAS, the actual implementation for time machine done by option in SMB sharing, named Multi-user time machine, so select Multi-user time machine as Purpose, otherwise, Time Machine option will not be set and it is unchangable.

Beware of option Time Machine is selected, and Path Suffix is set to %U, both are unchangable. The %U means, a sub-dataset will be created under shared dataset for each user, they will not share the same view.

The individual host to be backed up will create a folder <hostname>.sparsebundle, which will be shown as disk in MacOS.

File/Folder permission

Remove ACL

If got strange issue on permission, uncheck ACL in SMB sharing, and then restart SMB service.

Note: The error can be verified by using Windows access share drive.

Workable permission

The actual file created in sub-dataset, will be under builtin_users group with permission 770, not tm for unknown reason. Sample output is shown below.

truenas# ls -la /mnt/pool2/timemachine/tm
total 70
drwxrwx---+ 3 tm tm               4 Oct  3 22:32 .
drwxrwxr-x+ 6 tm tm               6 Oct  3 21:23 ..
-rwxrwx---+ 1 tm builtin_users 6148 Oct  3 21:32 .DS_Store
drwxrwx---+ 4 tm builtin_users   10 Oct  3 23:02 shark.sparsebundle
truenas#

Update

Suddently, timemachine on TrueNAS stopped working, error message shows macOS could not find server.

I tried to manually map SMB drive, but failed too. I could not access the timemachine shared folder, but rest of shared folders are accessible.

mDNS

During the troubleshooting, found that macOS could not see TrueNAS in Finder, the issue could be related to mDNS missing.

Finial settings

The following settings make timemachine work again.

  • Purpose: Multi-user time machine
  • Enable ACL
  • Browsable to Network Clients
  • Time Machine (Can not change)
  • Legacy AFP compatibility
  • Enable Shadow Copies
  • Enable Alternate Data Streams
  • Enable SMB2/3 Durable Handles

But the the shared folder still requires to be opened before macOS Time Machine can see it. So, mDNS issue is still there.

Migrate Storage from FreeNAS/TrueNAS Core to TrueNAS Scale

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Migrate Storage from FreeNAS/TrueNAS Core to TrueNAS Scale

Consideration

FreeNAS/TrueNAS Core is using FreeBSD OS, which doesn't support docker and KVM, it uses bhyve as Hyperviser. In order to use docker, requires VM to be installed, such as Rancher OS VM, which is an overhead of the system.

TrueNAS Scale is developed under Debian, and which is still under beta version. In order to use more features under virtualization, TrueNAS Scale is considered to be used.

Reinstall TrueNAS Scale

Installation of TrueNAS Scale is slower than TrueNAS Core, network configuration is different too.

Network

Network aggregation configuration for failover, could not select active and stand by interface. Need to find out more on this configuration.

Import TureNAS Core storage

ZFS pool can be installed easily.

Rename zpool name and dataset

To change the pool name, can use shell to import and export before use GUI import. Following commands can be used

zpool import pool_old pool_new
zpool export pool_new
zpool import pool_new
zfs rename old_name new_name
zpool export pool_new

The BSD hypervisor (bhyve) Basic

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The BSD hypervisor (bhyve) Basic

The BSD hypervisor, bhyve, pronounced "beehive" is a hypervisor/virtual machine manager available on FreeBSD, macOS, and Illumos.

FreeNAS® VMs use the bhyve(8) virtual machine software. This type of virtualization requires an Intel processor with Extended Page Tables (EPT) or an AMD processor with Rapid Virtualization Indexing (RVI) or Nested Page Tables (NPT).

To verify that an Intel processor has the required features, use Shell to run grep VT-x /var/run/dmesg.boot. If the EPT and UG features are shown, this processor can be used with bhyve.

To verify that an AMD processor has the required features, use Shell to run grep POPCNT /var/run/dmesg.boot. If the output shows the POPCNT feature, this processor can be used with bhyve.

References

The BSD hypervisor
FreeNAS VM

SSD Cache Basic

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SSD Cache Basic

Consideration

SSD cache helps accessing same set of files frequently. But if the system just holding media files, most likely they won't be visited again, then cache doesn't help.

RAM is required for SSD cache, but adding RAM is more directly impact the perform, because there is no duplication between harddisk and SSD.

Synolog

The required amount of RAM is calculated before cache created.

One SSD disk only can be configured for one volume in read-only mode.

Two or more SSD disks can be configured as one raid, for one volume in read-write mode.

Currently, one SSD disk or raid can not be partitioned for different volume.

FreeNAS/TrueNAS (Untested)

Others suggest 64GB or more of RAM before adding a cache, otherwise, will slow the system down if add a cache with 16GB RAM.

Fusion disk could be another choise because the SSD can be used as storage as well, no waste of space.

Fusion Pools Basic

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Fusion Pools Basic

Fusion Pools are also known as ZFS Allocation Classes, ZFS Special vdevs, and Metadata vdevs.

vdev

A special vdev can store meta data such as file locations and allocation tables. The allocations in the special class are dedicated to specific block types. By default, this includes all metadata, the indirect blocks of user data, and any deduplication tables. The class can also be provisioned to accept small file blocks. This is a great use case for high performance but smaller sized solid-state storage. Using a special vdev drastically speeds up random I/O and cuts the average spinning-disk I/Os needed to find and access a file by up to half.

Creating a Fusion Pool

Go to Storage > Pools, click ADD, and select Create new pool.

A pool must always have one normal (non-dedup/special) vdev before other devices can be assigned to the special class. Configure the Data VDevs, then click ADD VDEV and select Metadata.

Add SSDs to the new Metadata VDev and select the same layout as the Data VDevs.

Using a Mirror layout is possible, but it is strongly recommended to keep the layout identical to the other vdevs. If the special vdev fails and there is no redundancy, the pool becomes corrupted and prevents access to stored data.

When more than one metadata vdev is created, then allocations are load-balanced between all these devices. If the special class becomes full, then allocations spill back into the normal class.

After the fusion pool is created, the Status shows a Special section with the metadata SSDs.

Auto TRIM allows TrueNAS to periodically check the pool disks for storage blocks that can be reclaimed. This can have a performance impact on the pool, so the option is disabled by default. For more details about TRIM in ZFS, see the autotrim property description in zpool.8.

References

Fusion Pools