Cannot find snap-exec when fedora29 is the only installed base

[Zygmunt Krynicki]

On a system where snapd is installed from a distribution package (Fedora 29), using the "hello-fedora" and "fedora29" snaps (app, and base respectively) snapd incorrectly looks for snap-exec in the core snap that is not installed.

Base snaps should use the distribution provided snap-exec and snapctl in absence of the core snap.

[Michael Vogt (mvo)]

This should work - it sounds like a issue of "/usr/lib/snapd/snap-exec" vs "/usr/libexec/snapd/snap-exec" maybe?

[Zygmunt Krynicki (zyga)]

Installing fedora29 from the beta channel and hello-fedora from stable on Fedora 29 Workstation, running snapd 2.36.1 I get the following behaviour:

[zyga@localhost ~]$ snap version
snap 2.36-1.fc29
snapd 2.36-1.fc29
series 16
fedora 29
kernel 4.18.17-300.fc29.x86_64

[zyga@localhost ~]$ sudo snap install fedora29 --beta
fedora29 (beta) 2018.11.06 from Zygmunt Krynicki (zygoon) installed

[zyga@localhost ~]$ sudo snap install hello-fedora
hello-fedora 0.1 from Zygmunt Krynicki (zygoon) installed

[zyga@localhost ~]$ snap run hello-fedora
cannot locate the core snap: No such file or directory

[zyga@localhost ~]$ SNAPD_DEBUG=1 snap run hello-fedora
2018/11/14 19:17:36.474709 cmd_linux.go:70: DEBUG: re-exec not supported on distro "fedora" yet
DEBUG: security tag: snap.hello-fedora.hello-fedora
DEBUG: executable: /usr/lib/snapd/snap-exec
DEBUG: confinement: non-classic
DEBUG: base snap: fedora29
DEBUG: ruid: 1000, euid: 0, suid: 0
DEBUG: rgid: 1000, egid: 0, sgid: 0
DEBUG: checking if the current process shares mount namespace with the init process
DEBUG: re-associating is not required
DEBUG: creating lock directory /run/snapd/lock (if missing)
DEBUG: opening lock directory /run/snapd/lock
DEBUG: opening lock file: /run/snapd/lock/.lock
DEBUG: sanity timeout initialized and set for three seconds
DEBUG: acquiring exclusive lock (scope (global), uid 0)
DEBUG: sanity timeout reset and disabled
DEBUG: ensuring that snap mount directory is shared
DEBUG: unsharing snap namespace directory
DEBUG: creating namespace group directory /run/snapd/ns
DEBUG: namespace group directory does not require intialization
DEBUG: releasing lock 4
DEBUG: snap-update-ns executable: /usr/libexec/snapd/snap-update-ns
DEBUG: opened snap-update-ns executable as file descriptor 3
DEBUG: creating lock directory /run/snapd/lock (if missing)
DEBUG: opening lock directory /run/snapd/lock
DEBUG: opening lock file: /run/snapd/lock/hello-fedora.lock
DEBUG: sanity timeout initialized and set for three seconds
DEBUG: acquiring exclusive lock (scope hello-fedora, uid 0)
DEBUG: sanity timeout reset and disabled
DEBUG: initializing mount namespace: hello-fedora
DEBUG: opening namespace group directory /run/snapd/ns
DEBUG: initializing new namespace group hello-fedora
DEBUG: forking support process for mount namespace capture
DEBUG: forked support process has pid 4090
DEBUG: forked support process has pid 0
DEBUG: changing apparmor hat of the support process for mount namespace capture
DEBUG: ensuring that parent process is still alive
DEBUG: waiting for a eventfd data from the parent process to continue
DEBUG: sanity timeout initialized and set for three seconds
DEBUG: unsharing the mount namespace
DEBUG: scratch directory for constructing namespace: /tmp/snap.rootfs_QsegOH
DEBUG: performing operation: (disabled) use debug build to see details
DEBUG: performing operation: (disabled) use debug build to see details
DEBUG: performing operation: (disabled) use debug build to see details
DEBUG: performing operation: (disabled) use debug build to see details
DEBUG: performing operation: (disabled) use debug build to see details
DEBUG: performing operation: (disabled) use debu...

[Zygmunt Krynicki (zyga)]

This should be fixed with the following PR https://github.com/snapcore/snapd/pull/6123