Restarting systemd-sysext service creates additional loop devices

[jo5huajohn]

I suspect this is related to systemd-sysext, but I noticed that in addition to the existing loop devices created during the first boot of the systemd-sysext service, new loop devices were created each time I restarted the systemd-sysext service. Is this expected behavior? Shouldn't the existing loop devices be removed prior to creating new ones? Running Fedora 42 Silverblue. How can I debug this?

joshua@fedora:~$ lsblk
NAME        MAJ:MIN RM   SIZE RO TYPE MOUNTPOINTS                                                                                                                                                                   
loop0         7:0    0   928K  1 loop                                                                                                                                                                               
loop1         7:1    0   2.9M  1 loop                                                                                                                                                                               
loop2         7:2    0   372K  1 loop                                                                                                                                                                               
loop3         7:3    0   1.6M  1 loop                                                                                                                                                                               
loop4         7:4    0   3.7M  1 loop                                                                                                                                                                               
loop5         7:5    0  26.5M  1 loop                                                                                                                                                                               
loop6         7:6    0  24.5M  1 loop                                                                                                                                                                               
loop7         7:7    0  25.3M  1 loop                                                                                                                                                                               
zram0       251:0    0     8G  0 disk [SWAP]                                                                                                                                                                        
nvme0n1     259:0    0 465.8G  0 disk                                                                                                                                                                               
├─nvme0n1p1 259:1    0   100M  0 part 
├─nvme0n1p2 259:2    0    16M  0 part 
├─nvme0n1p3 259:3    0   465G  0 part 
└─nvme0n1p4 259:4    0   642M  0 part 
nvme1n1     259:5    0 465.8G  0 disk 
├─nvme1n1p1 259:6    0   600M  0 part /boot/efi
├─nvme1n1p2 259:7    0     1G  0 part /boot
└─nvme1n1p3 259:8    0 464.2G  0 part /var/home
                                      /var
                                      /sysroot/ostree/deploy/fedora/var
                                      /etc
                                      /sysroot

joshua@fedora:~$ sudo systemctl restart systemd-sysext.service

joshua@fedora:~$ lsblk
NAME        MAJ:MIN RM   SIZE RO TYPE MOUNTPOINTS
loop0         7:0    0   928K  1 loop 
loop1         7:1    0   2.9M  1 loop 
loop2         7:2    0   372K  1 loop 
loop3         7:3    0   1.6M  1 loop 
loop4         7:4    0   3.7M  1 loop 
loop5         7:5    0  26.5M  1 loop 
loop6         7:6    0  24.5M  1 loop 
loop7         7:7    0  25.3M  1 loop 
loop8         7:8    0  26.5M  1 loop 
loop9         7:9    0   928K  1 loop 
loop10        7:10   0   1.6M  1 loop 
loop11        7:11   0   3.7M  1 loop 
loop12        7:12   0  25.3M  1 loop 
loop13        7:13   0   2.9M  1 loop 
loop14        7:14   0   372K  1 loop 
loop15        7:15   0  24.5M  1 loop 
zram0       251:0    0     8G  0 disk [SWAP]
nvme0n1     259:0    0 465.8G  0 disk 
├─nvme0n1p1 259:1    0   100M  0 part 
├─nvme0n1p2 259:2    0    16M  0 part 
├─nvme0n1p3 259:3    0   465G  0 part 
└─nvme0n1p4 259:4    0   642M  0 part 
nvme1n1     259:5    0 465.8G  0 disk 
├─nvme1n1p1 259:6    0   600M  0 part /boot/efi
├─nvme1n1p2 259:7    0     1G  0 part /boot
└─nvme1n1p3 259:8    0 464.2G  0 part /var/home
                                      /var
                                      /sysroot/ostree/deploy/fedora/var
                                      /etc
                                      /sysroot


joshua@fedora:~$ sudo systemctl restart systemd-sysext.service

joshua@fedora:~$ lsblk
NAME        MAJ:MIN RM   SIZE RO TYPE MOUNTPOINTS
loop0         7:0    0   928K  1 loop 
loop1         7:1    0   2.9M  1 loop 
loop2         7:2    0   372K  1 loop 
loop3         7:3    0   1.6M  1 loop 
loop4         7:4    0   3.7M  1 loop 
loop5         7:5    0  26.5M  1 loop 
loop6         7:6    0  24.5M  1 loop 
loop7         7:7    0  25.3M  1 loop 
loop8         7:8    0  26.5M  1 loop 
loop9         7:9    0   928K  1 loop 
loop10        7:10   0   1.6M  1 loop 
loop11        7:11   0   3.7M  1 loop 
loop12        7:12   0  25.3M  1 loop 
loop13        7:13   0   2.9M  1 loop 
loop14        7:14   0   372K  1 loop 
loop15        7:15   0  24.5M  1 loop 
loop16        7:16   0   372K  1 loop 
loop17        7:17   0   3.7M  1 loop 
loop18        7:18   0  24.5M  1 loop 
loop19        7:19   0   2.9M  1 loop 
loop20        7:20   0   928K  1 loop 
loop21        7:21   0  25.3M  1 loop 
loop22        7:22   0   1.6M  1 loop 
loop23        7:23   0  26.5M  1 loop 
zram0       251:0    0     8G  0 disk [SWAP]
nvme0n1     259:0    0 465.8G  0 disk 
├─nvme0n1p1 259:1    0   100M  0 part 
├─nvme0n1p2 259:2    0    16M  0 part 
├─nvme0n1p3 259:3    0   465G  0 part 
└─nvme0n1p4 259:4    0   642M  0 part 
nvme1n1     259:5    0 465.8G  0 disk 
├─nvme1n1p1 259:6    0   600M  0 part /boot/efi
├─nvme1n1p2 259:7    0     1G  0 part /boot
└─nvme1n1p3 259:8    0 464.2G  0 part /var/home
                                      /var
                                      /sysroot/ostree/deploy/fedora/var
                                      /etc
                                      /sysroot

[jo5huajohn]

Output of systemd-sysext status:

joshua@fedora:~$ systemd-sysext status
HIERARCHY EXTENSIONS  SINCE                      
/opt      none        -                          
/usr      distrobox   Tue 2025-07-15 22:37:07 +04
          erofs-utils 
          just        
          neovim      
          tailscale   
          tmux        
          vim         
          zoxide  

[travier]

It needs one loop device per sysext until support for direct file backed mount is used in systemd-sysext:

• mount: Support EROFS file-backed mounts composefs/composefs#403
• mount: add support for optionally skipping loopback device composefs/composefs#361
• better loopback handling (hiding it) composefs/composefs#144
• https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=fb176750266a

Or we re-implement the refresh operation in https://github.com/travier/sysexts-manager.