How can I use ln -s to to make a symlink to the Geth chaindata on an external SD card?

I download the Geth chaindata to an external SD card to relieve the internal hard drive from the hard work.

However, I cannot start Mist when Geth is downloading the chaindata to an external SD card.

Luclu @ Ethereum confirmed that it should be possible to use a symlink to the SD card chaindata to allow Mist to run with this configuration.

What should the ln -s command look like?

OS: Ubuntu 15.10

  • Note, it will take ages to sync the chain to an sd card, why not getting a small external SSD?
    – q9f
    Jun 3, 2016 at 8:08
  • Actually, that doesn't seem to be the case. It does not seem slow. Could be that the bottleneck is elsewhere than the SD i/o writing speed.
    – Vesa
    Jun 4, 2016 at 10:30

2 Answers 2


You can either store the whole .ethereum folder or only .etereum/chaindata there

In -s <path to chain on ext drive> ~/.ethereum/chaindata
  • I tried to do it with only the chaindata but I was not able to start Mist afterwards
    – Vesa
    Jun 3, 2016 at 8:49
  • You would have to remove the old chaindata folder in .ethereum first. have you? Jun 3, 2016 at 8:50
  • ls -lha ~/.ethereum what does it show? Should have a line like: lrwxrwxrwx 1 roland roland 32 apr 25 09:33 chaindata -> /media/roland/SAMSUNG2/chaindata Jun 3, 2016 at 8:52
  • It does have that. But it still didn't work last time I tried.
    – Vesa
    Jun 4, 2016 at 10:32

Assuming you are using some kind of linux/unix, this might also work for mac osx, but I'm unsure if the syntax is the same.

Mount your external medium:

sudo mkdir -p /mnt/sdcard
sudo mount /dev/sdX1 /mnt/sdcard

Create a symbolic link for the chaindata:

ln -s /mnt/sdcard ~/.ethereum/chaindata


  1. This has to be done before the first start of geth.
  2. Whenever you reboot your computer and want to start geth again, make sure the sdcard is mounted!
  • Why does it have to be done before the first start of Geth? Isn't it enough just to remove any previous chaindata folder and start resyncing?
    – Vesa
    Jun 3, 2016 at 8:50
  • @Vesa yes, deleting the data will do fine.
    – JasoonS
    Aug 27, 2017 at 10:15
  • After symlinking the folder that geth is writing too is out of space even though the symlinked dir has plenty of space, how do you resolve this?
    – foba
    Jan 28, 2021 at 17:56

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