Increase disk space on DietPi

I have been unable to update my DietPi installation for some time now because of disk space constraints. I finally looked into it and here is what I found.

If you do not care to read (or about) all the words and explanations, feel free to skip to the SHORT VERSION

BACKGROUND

For some reasons that I should really re-evaluate, I installed DietPi on my very early Raspberry Pi (I’ll have to search my archives because I remember researching the version at some point…but suffice it to say that this thing is very rudimentary). Well, basically ever since that initial installation, it has told me there was an update available.

However, every attempt to run dietpi-update resulted in an error stating that there was not enough disk space available for the update (I don’t recall the exact error wording, sorry about that). This was puzzling to me because I do not have much running on this system other than Pi-hole for network-wide ad blocking. I do not know much about how this service functions, but I was surprised that it might be the reason I don’t have any disk space.

After poking around on the command line I eventually found that, by default, the DietPi installation had created and was using a ~1.8G swap file. There are endless articles on swap recommendations and I’m sure that DietPi adheres to one such recommendation…but my entire disk is only 4G so you can see why this doesn’t work for my situation. (This post is not going to make any commentary on how large swap should be or get into any details of what swap is because the internet abounds with this sort of data: see here for a start.)

CHALLENGE

I found some hints online that indicated I should use the nice TUI that is provided by DietPi to change the size of swap, that’s the point after all, isn’t it: to make this whole thing more user-friendly. Well I couldn’t select the right order of menu items to modify swap like I needed to…but I have spent the majority of my career on a command line and know how to modify swap there!

SOLUTION

01 ensure that swap isn’t being used

In my case, out of the 1.8G allocated for swap, 0B was being used:

root@DietPi:~# swapon
NAME      TYPE  SIZE USED PRIO
/var/swap file 1.8G    0B   -2                # <--- 1.8G but 0B used...
root@DietPi:~# free -m
              total        used        free      shared  buff/cache   available
Mem:            227          37          39          36         150          89
Swap:          1820           0        1820   # <--- 0 used

02 turn swap “off”

We need to “disable” or turn swap “off” so that nothing attempts to use it:

root@DietPi:~# swapoff -a

03 free up the space swap was using

There are a lot of ways to configure swap, but the DietPi installation utilizes a swap file so we will delete that file:

root@DietPi:~# grep swap /etc/fstab
/var/swap    none    swap    sw    0   0                  # <--- see /var/swap
root@DietPi:~# ls -l /var/swap
-rw------- 1 root root 1909456896 Aug  2  2018 /var/swap  # <--- note the size
root@DietPi:~# rm -vfr /var/swap 
removed '/var/swap'

04 create a new swap file

The simplest strategy here is to reuse the file name that DietPi is expecting, but just use a smaller file. I decided to use 1G (for no real reason):

root@DietPi:~# fallocate -l 1G /var/swap  # <--- I used 1G, use what feels right
root@DietPi:~# chmod 0600 /var/swap       # <--- set the perms correctly
root@DietPi:~# mkswap /var/swap           # <--- label it as swap
Setting up swapspace version 1, size = 1024 MiB (1073737728 bytes)
no label, UUID=ce36cdd7-2c9d-4bfa-bf27-3a291fa91664

05 turn swap back “on”

Since we reused the filename, everything should just work as expected after we reduced the size of the swap file, re-enable it:

root@DietPi:~# swapon -a
root@DietPi:~# free -m
              total        used        free      shared  buff/cache   available
Mem:            227          38          36          36         152          88
Swap:          1023           0        1023   # <--- new size
root@DietPi:~# swapon
NAME      TYPE  SIZE USED PRIO
/var/swap file 1024M   0B   -2                # <--- 1024M now

NEXT STEPS

• hopefully, after reducing the swap file size, there is enough space to execute the dietpi-update (it was enough for me)…and keep in mind that the update might take a while if you missed as many updates as I did…

SIDE NOTES

• I do not log into this thing very often, which is part of the reason this was never addressed previously. That’s the point of treating it as an appliance, right?!
• I do not know what effect reducing the swap size will be, I’m sure the default size was picked for a reason, but I’m too cheap to use a larger disk
• If you find that swap is actually being used in your case you may need to take some different steps, but I really don’t think that disabling it momentarily and reducing the size will make that big of a difference…but YMMV

WHAT I LEARNED

• this is still a great use for my old hardware, I just needed to do some things that DietPi might not have wanted…

REFERENCE

• N/A

SHORT VERSION

To avoid tl;dr enjoy this instead:

#### 01 ensure that swap isn't being used
root@DietPi:~# swapon
NAME      TYPE  SIZE USED PRIO
/var/swap file 1.8G    0B   -2                # <--- 1.8G but 0B used...
root@DietPi:~# free -m
              total        used        free      shared  buff/cache   available
Mem:            227          37          39          36         150          89
Swap:          1820           0        1820   # <--- 0 used
#### 02 turn swap "off"
root@DietPi:~# swapoff -a
#### 03 free up the space swap was using
root@DietPi:~# grep swap /etc/fstab
/var/swap    none    swap    sw    0   0                  # <--- see /var/swap
root@DietPi:~# ls -l /var/swap
-rw------- 1 root root 1909456896 Aug  2  2018 /var/swap  # <--- note the size
root@DietPi:~# rm -vfr /var/swap 
removed '/var/swap'
#### 04 create a new swap file
root@DietPi:~# fallocate -l 1G /var/swap  # <--- I used 1G, use what feels right
root@DietPi:~# chmod 0600 /var/swap       # <--- set the perms correctly
root@DietPi:~# mkswap /var/swap           # <--- label it as swap
Setting up swapspace version 1, size = 1024 MiB (1073737728 bytes)
no label, UUID=ce36cdd7-2c9d-4bfa-bf27-3a291fa91664
#### 05 turn swap back "on"
root@DietPi:~# swapon -a
root@DietPi:~# free -m
              total        used        free      shared  buff/cache   available
Mem:            227          38          36          36         152          88
Swap:          1023           0        1023   # <--- new size
root@DietPi:~# swapon
NAME      TYPE  SIZE USED PRIO
/var/swap file 1024M   0B   -2                # <--- 1024M now