Lately I’ve been having issues upgrading the DSM version on my Synology DS418 play. The updater refused to download/start the update with the error “Insufficient system capacity for update”.

The previous time I had this error I tried messing around with files on my root partition until the error disappeared. I can’t remember the details but it was a lot of trial and error, and in general shouldn’t be necessary.

But today I got the same error when trying to do another update. According to Synology support, the issue might be caused by third party packages that install files somewhere where they shouldn’t. I thought this might be because I installed docker, since that’s not “officially” supported but I really didn’t wanted to get rid of it (or remove it temporarily in the first place). And since it’s still sort of an official package, just not findable by default, I assumed it would behave properly.

Analyzing disk usage

The total space used on the root partition was near 2GB

root@/: # df -h
Filesystem      Size  Used Avail Use% Mounted on
/dev/md0        2.3G  1.9G  345M  85% /
devtmpfs        3.9G     0  3.9G   0% /dev
tmpfs           3.9G  236K  3.9G   1% /dev/shm
tmpfs           3.9G   15M  3.8G   1% /run
tmpfs           3.9G     0  3.9G   0% /sys/fs/cgroup
tmpfs           3.9G  2.1M  3.9G   1% /tmp
/dev/vg1000/lv  3.5T  965G  2.6T  28% /volume1

However, when summing up all directories in the root

root@/: # du -hs usr config dev etc etc.defaults initrd lost+found mnt opt root run tmp usr var var.defaults
996M	usr
0	config
236K	dev
3.6M	etc
2.4M	etc.defaults
4.0K	initrd
4.0K	lost+found
4.0K	mnt
16K	opt
28K	root
15M	run
2.1M	tmp
145M	var
5.8M	var.defaults

Summing these values 996+1+4+3+15+2+145+6, I got 1.2GB at most. Over a gig, but not near 2 GB.

Then I realized I completely ignored .dotfiles

root@/: # du -hs .??*
677M	.SynoUpgrade.tar
1.6M	.log.junior
36K	.old_patch_info
4.0K	.rnd
32M	.syno
20K	.system_info

and I noticed a rather old .SynoUpgrade.tar

root@Sien:/ # ls -lh .SynoUpgrade.tar
-rw-r--r-- 1 root root 681M Sep 13  2020 .SynoUpgrade.tar

So probably an old update that somehow didn’t get removed. Moving it to the storage partition I ended up with the expected 1.2GB of usage, and the install could continue :)

root@/: # df -h
Filesystem      Size  Used Avail Use% Mounted on
/dev/md0        2.3G  1.2G 1022M  54% /
...

Howver, after the update I noticed I was low on space again

root@/: # df -h
Filesystem      Size  Used Avail Use% Mounted on
/dev/md0        2.3G  1.7G  541M  76% /
...

Looking around for another install tarbal left behind, I quickly found a large file, space-preserve in /usr/syno/synoinstall

root@/usr/syno/synoinstall/: # ls -lh
total 497M
-rw-r--r-- 1 root root 513M Sep 11 10:26 space-preserve

but I suspect this file is actually meant to “claim” the space that’s required for upgrades so I’ll leave it for now and see if the error reappears during a later upgrade.

TL;DR

If you get the error “insufficient system capacity for update”, check if you have an old .SynoUpdate.tar in your /