Questions[snapshot](ubuntu)

I started to get "not enough free space" errors when trying to copy files, and at some point I had trouble booting and did a ZFS rollback. I still get space errors despite (according to df and du below) <60% drive space being used.

The answer below points to zfs snapshots taking up too much space, and it's a helpful start. But sudo du /.zfs/snapshot/ -h --max-depth=0 returns only 60G. Are there 140G of snapshots elsewhere? (or what else could it be?)

Also conspicuously zfs list -t snapshot doesn't show the (biggest and I assume most defunct?) dataset rpool/USERDATA/thomas_fv2wpz which is shown in zfs list output below to be 278G.

Here's a table of contents for outputs:

• uname -a
• zfs list
• zfs list -o space rpool/USERDATA
• Should I omit (some/parts of) the following long outputs? this my first time asking a question.
• df -h
• du -h --max-depth=1
• lsblk -f

$ uname -a
Linux thomas-Latitude-E6530 5.4.0-31-generic #35-Ubuntu SMP Thu May 7 20:20:34 UTC 2020 x86_64 x86_64 x86_64 GNU/Linux

$ zfs list
NAME                                               USED  AVAIL     REFER  MOUNTPOINT
bpool                                              272M  1.48G       96K  /boot
bpool/BOOT                                         270M  1.48G       96K  none
bpool/BOOT/ubuntu_nhdx6z                           270M  1.48G      180M  /boot
bpool/BOOT/ubuntu_smztg7                             8K  1.48G      180M  /boot
rpool                                              441G  4.89G       96K  /
rpool/ROOT                                        8.97G  4.89G       96K  none
rpool/ROOT/ubuntu_nhdx6z                          8.51G  4.89G     3.69G  /
rpool/ROOT/ubuntu_nhdx6z/srv                       264K  4.89G       96K  /srv
rpool/ROOT/ubuntu_nhdx6z/usr                       872K  4.89G       96K  /usr
rpool/ROOT/ubuntu_nhdx6z/usr/local                 776K  4.89G      144K  /usr/local
rpool/ROOT/ubuntu_nhdx6z/var                      3.24G  4.89G       96K  /var
rpool/ROOT/ubuntu_nhdx6z/var/games                 152K  4.89G       96K  /var/games
rpool/ROOT/ubuntu_nhdx6z/var/lib                  3.10G  4.89G     2.74G  /var/lib
rpool/ROOT/ubuntu_nhdx6z/var/lib/AccountsService   688K  4.89G      104K  /var/lib/AccountsService
rpool/ROOT/ubuntu_nhdx6z/var/lib/NetworkManager   1.76M  4.89G      164K  /var/lib/NetworkManager
rpool/ROOT/ubuntu_nhdx6z/var/lib/apt              70.1M  4.89G     53.6M  /var/lib/apt
rpool/ROOT/ubuntu_nhdx6z/var/lib/dpkg             97.8M  4.89G     39.4M  /var/lib/dpkg
rpool/ROOT/ubuntu_nhdx6z/var/log                   138M  4.89G     36.4M  /var/log
rpool/ROOT/ubuntu_nhdx6z/var/mail                  152K  4.89G       96K  /var/mail
rpool/ROOT/ubuntu_nhdx6z/var/snap                 1.31M  4.89G      240K  /var/snap
rpool/ROOT/ubuntu_nhdx6z/var/spool                 848K  4.89G      120K  /var/spool
rpool/ROOT/ubuntu_nhdx6z/var/www                   152K  4.89G       96K  /var/www
rpool/ROOT/ubuntu_smztg7                           471M  4.89G     3.18G  /
rpool/ROOT/ubuntu_smztg7/srv                        56K  4.89G       96K  /srv
rpool/ROOT/ubuntu_smztg7/usr                       144K  4.89G       96K  /usr
rpool/ROOT/ubuntu_smztg7/usr/local                 144K  4.89G      144K  /usr/local
rpool/ROOT/ubuntu_smztg7/var                       203M  4.89G       96K  /var
rpool/ROOT/ubuntu_smztg7/var/games                 112K  4.89G       96K  /var/games
rpool/ROOT/ubuntu_smztg7/var/lib                   177M  4.89G     2.65G  /var/lib
rpool/ROOT/ubuntu_smztg7/var/lib/AccountsService   144K  4.89G      104K  /var/lib/AccountsService
rpool/ROOT/ubuntu_smztg7/var/lib/NetworkManager    320K  4.89G      148K  /var/lib/NetworkManager
rpool/ROOT/ubuntu_smztg7/var/lib/apt              4.08M  4.89G     53.3M  /var/lib/apt
rpool/ROOT/ubuntu_smztg7/var/lib/dpkg             14.0M  4.89G     39.4M  /var/lib/dpkg
rpool/ROOT/ubuntu_smztg7/var/log                  24.9M  4.89G     15.0M  /var/log
rpool/ROOT/ubuntu_smztg7/var/mail                  112K  4.89G       96K  /var/mail
rpool/ROOT/ubuntu_smztg7/var/snap                  212K  4.89G      188K  /var/snap
rpool/ROOT/ubuntu_smztg7/var/spool                 160K  4.89G      120K  /var/spool
rpool/ROOT/ubuntu_smztg7/var/www                   112K  4.89G       96K  /var/www
rpool/USERDATA                                     432G  4.89G       96K  /
rpool/USERDATA/helper_zthl10                       180K  4.89G      124K  /home/helper
rpool/USERDATA/root_fv2wpz                         316K  4.89G     1.12M  /root
rpool/USERDATA/root_mhe8ya                        1.78M  4.89G      992K  /root
rpool/USERDATA/thomas_fv2wpz                       971M  4.89G      278G  /home/thomas
rpool/USERDATA/thomas_mhe8ya                       431G  4.89G      217G  /home/thomas

$ zfs list -o space rpool/USERDATA
NAME            AVAIL   USED  USEDSNAP  USEDDS  USEDREFRESERV  USEDCHILD
rpool/USERDATA  4.88G   432G        0B     96K             0B       432G

$ df -h
Filesystem                                        Size  Used Avail Use% Mounted on
udev                                              5.8G     0  5.8G   0% /dev
tmpfs                                             1.2G  2.1M  1.2G   1% /run
rpool/ROOT/ubuntu_nhdx6z                          8.8G  3.7G  5.1G  42% /
tmpfs                                             5.8G  253M  5.6G   5% /dev/shm
tmpfs                                             5.0M  4.0K  5.0M   1% /run/lock
tmpfs                                             5.8G     0  5.8G   0% /sys/fs/cgroup
rpool/USERDATA/helper_zthl10                      5.1G  128K  5.1G   1% /home/helper
bpool/BOOT/ubuntu_nhdx6z                          1.7G  180M  1.5G  11% /boot
rpool/USERDATA/thomas_fv2wpz                      284G  279G  5.1G  99% /home/thomas
rpool/USERDATA/root_fv2wpz                        5.1G  1.0M  5.1G   1% /root
rpool/ROOT/ubuntu_nhdx6z/srv                      5.1G  128K  5.1G   1% /srv
rpool/ROOT/ubuntu_nhdx6z/var/games                5.1G  128K  5.1G   1% /var/games
rpool/ROOT/ubuntu_nhdx6z/var/log                  5.2G   29M  5.1G   1% /var/log
rpool/ROOT/ubuntu_nhdx6z/var/lib                  7.9G  2.8G  5.1G  35% /var/lib
rpool/ROOT/ubuntu_nhdx6z/usr/local                5.1G  256K  5.1G   1% /usr/local
rpool/ROOT/ubuntu_nhdx6z/var/mail                 5.1G  128K  5.1G   1% /var/mail
rpool/ROOT/ubuntu_nhdx6z/var/www                  5.1G  128K  5.1G   1% /var/www
/dev/sda1                                         511M  7.1M  504M   2% /boot/efi
rpool/ROOT/ubuntu_nhdx6z/var/snap                 5.1G  256K  5.1G   1% /var/snap
rpool/ROOT/ubuntu_nhdx6z/var/spool                5.1G  128K  5.1G   1% /var/spool
rpool/ROOT/ubuntu_nhdx6z/var/lib/AccountsService  5.1G  128K  5.1G   1% /var/lib/AccountsService
/dev/loop2                                         62M   62M     0 100% /snap/caprine/36
/dev/loop3                                         55M   55M     0 100% /snap/core18/1754
/dev/loop4                                        176M  176M     0 100% /snap/gimp/273
/dev/loop0                                        9.2M  9.2M     0 100% /snap/canonical-livepatch/95
/dev/loop5                                        241M  241M     0 100% /snap/gnome-3-34-1804/24
rpool/ROOT/ubuntu_nhdx6z/var/lib/dpkg             5.2G   40M  5.1G   1% /var/lib/dpkg
rpool/ROOT/ubuntu_nhdx6z/var/lib/apt              5.2G   54M  5.1G   2% /var/lib/apt
rpool/ROOT/ubuntu_nhdx6z/var/lib/NetworkManager   5.1G  256K  5.1G   1% /var/lib/NetworkManager
/dev/loop7                                        174M  174M     0 100% /snap/gimp/252
/dev/loop6                                         94M   94M     0 100% /snap/core/9066
/dev/loop1                                         55M   55M     0 100% /snap/core18/1705
/dev/loop8                                        164M  164M     0 100% /snap/spotify/41
/dev/loop9                                        256K  256K     0 100% /snap/gtk2-common-themes/9
/dev/loop10                                       143M  143M     0 100% /snap/slack/23
/dev/loop11                                       256M  256M     0 100% /snap/gnome-3-34-1804/33
/dev/loop13                                        63M   63M     0 100% /snap/gtk-common-themes/1506
/dev/loop12                                        28M   28M     0 100% /snap/snapd/7264
/dev/loop14                                        50M   50M     0 100% /snap/snap-store/454
/dev/loop15                                       142M  142M     0 100% /snap/zoom-client/83
/dev/loop16                                       161M  161M     0 100% /snap/gnome-3-28-1804/116
/dev/loop17                                        87M   87M     0 100% /snap/shotcut/64
/dev/loop18                                       291M  291M     0 100% /snap/vlc/1620
/dev/loop19                                       140M  140M     0 100% /snap/slack/24
/dev/loop20                                        50M   50M     0 100% /snap/snap-store/433
/dev/loop21                                       145M  145M     0 100% /snap/zoom-client/84
tmpfs                                             1.2G   52K  1.2G   1% /run/user/1000
/dev/loop22                                        64M   64M     0 100% /snap/caprine/37

$ du -h --max-depth=1
25K ./Music
1.0K    ./.ssh
1.0K    ./Templates
36K ./.gnome
30M ./.thunderbird
52M ./Documents
368M    ./snap
8.4M    ./.mozilla
203G    ./Pictures
302M    ./.config
1021M   ./.cache
1.0K    ./Public
9.5G    ./Downloads
101M    ./.local
7.0K    ./Steam
41G ./Videos
28K ./.gnupg
7.6G    ./Desktop
16G ./.steam
17K ./.pki
11K ./.psensor
279G    .

$ lsblk -f
NAME   FSTYPE     LABEL UUID                                 FSAVAIL FSUSE% MOUNTPOINT
loop0  squashfs                                                    0   100% /snap/canonical-livepatch/95
loop1  squashfs                                                    0   100% /snap/core18/1705
loop2  squashfs                                                    0   100% /snap/caprine/36
loop3  squashfs                                                    0   100% /snap/core18/1754
loop4  squashfs                                                    0   100% /snap/gimp/273
loop5  squashfs                                                    0   100% /snap/gnome-3-34-1804/24
loop6  squashfs                                                    0   100% /snap/core/9066
loop7  squashfs                                                    0   100% /snap/gimp/252
loop8  squashfs                                                    0   100% /snap/spotify/41
loop9  squashfs                                                    0   100% /snap/gtk2-common-themes/9
loop10 squashfs                                                    0   100% /snap/slack/23
loop11 squashfs                                                    0   100% /snap/gnome-3-34-1804/33
loop12 squashfs                                                    0   100% /snap/snapd/7264
loop13 squashfs                                                    0   100% /snap/gtk-common-themes/1506
loop14 squashfs                                                    0   100% /snap/snap-store/454
loop15 squashfs                                                    0   100% /snap/zoom-client/83
loop16 squashfs                                                    0   100% /snap/gnome-3-28-1804/116
loop17 squashfs                                                    0   100% /snap/shotcut/64
loop18 squashfs                                                    0   100% /snap/vlc/1620
loop19 squashfs                                                    0   100% /snap/slack/24
loop20 squashfs                                                    0   100% /snap/snap-store/433
loop21 squashfs                                                    0   100% /snap/zoom-client/84
loop22 squashfs                                                    0   100% /snap/caprine/37
sda                                                                         
├─sda1 vfat             105C-066C                             503.9M     1% /boot/efi
├─sda2                                                                      
├─sda5 swap             ca95a35a-589b-4127-91d0-ba74f05c7011                [SWAP]
├─sda6 zfs_member bpool 10888252588400514123                                
└─sda7 zfs_member rpool 8231086401312639965                                 
sr0   

I've installed Ubuntu 20.04 on a Btrfs root-partition for its snapshot functionality.

To keep it as simple as possible, I would like to integrate the creation of a Btrfs snapshot into my upgrade-alias command, which currently looks like this:

sudo apt update && sudo apt upgrade -y && sudo flatpak update -y && sudo snap refresh

How would I best add a snapshot before the updates so I can roll back if anything goes wrong?

Is there also a possiblity to remove older snapshots at the same time? (My root-partition is filled less than 10%, so I could copy my entire system multiple times, but I suppose it will fill up quickly with weekly updates?)

Context: I was thinking about making snapshot for safety reasons, so I downloaded Timeshift but once installed, I have to make a choice between Rsync and BTRFS Snapshots

I already read the documentation:

Question: But considering I'm really new to system restore point and snapshots, I can't figure out which one should I choose, and what's the difference ?

Following comments under this answer of mine I became interested in the question whether the best option for me in order to back-up a system is a partition back-up as described at the linked answer or a snapshot as created by Timeshift (which I have not yet used).

So, I know what a partition image is and how it can be created and restored, but I would like to know whether snapshots are a better option or not. I have some info about snapshots but I want to know more details on the differences between snapshots and partition isos as far as restoration is concerned.

I see that there are differences between the two types of snapshots created by Timeshift as they are clearly listed once the program starts.

As my system is on an ext4 partition (and I find preferable to save the snapshot on an external drive), the option that I will use for now is RSYNC. But I am interested about BTRFS, which I plan to use in the future.

The clarifications I need regard mainly the following aspects:

Do I have to run the very system that I have backed-up with Timeshift in order to restore the snapshot?

It seems to me that's the case, contrary to a partition saved as iso. In that case the system that I have just backed-up has to be functional and Timeshift installed in it in order to restore the back-up. But then what is the point of that back-up? Normally I want a back-up in case I lose the backed-up system. If the OS is lost, how can the snapshot be restored?

My idea of a back-up is to save a healthy well customized system that I could restore later when the running system has become bloated or unusable.

It seems to me that the purpose of a snapshot is to constantly make back-ups of the actual running system in its present state. But if the system is not in good health are these back-ups efficient? Or are the snapshots images of various stages/moments of the system that are ALL saved, including an initial, healthy and well-customized one? Even so, how is that to be restored if the running system is lost?

Or maybe I'm wrong and Snapshot can restore a system B onto a system A, thus replacing it?

I installed ubuntu without LVM. Is it still possible to make a snapshot of it? If so how can I do it? Keep in mind I never made a linux snapshot before.

Ubuntu 16.04 LTS, Kernel 4.5