[master] recommend fuse-overlayfs for Debian too

[AkihiroSuda]

Debian kernel has a non-upstream modprobe option permit_mounts_in_userns=1 for kernel-mode overlayfs, but seems unstable: moby/moby#42302

So we should recommend fuse-overlayfs for Debian (until the release of Debian 12, which will support genuine kernel-mode overlayfs with kernel >= 5.11).

[thaJeztah]

This control file is used for both Debian an Ubuntu; can we make this somehow conditional for Debian only? I recall we had some conditional rule for AppArmor on Debian that I removed in #487 - perhaps a similar rule would work for this?

[AkihiroSuda]

Modifying the file with echo ... >> control doesn't look robust. So I'd prefer to recommend fuse-overlayfs unconditionally.

[thaJeztah]

It's creating a .substvars file (not modifying the control file)

[thaJeztah]

@tianon PTAL; perhaps you have suggestions on how to make this conditional for Debian (but not Ubuntu) in a clean way?

[tianon]

Indeed - the approach that was removed in #487 (override_dh_gencontrol writing into debian/docker-ce-rootless-extras.substvars) is definitely "correct".

Something like this: (untested 😇)

diff --git a/deb/common/control b/deb/common/control
index 0b5ed4a..34de085 100644
--- a/deb/common/control
+++ b/deb/common/control
@@ -94,9 +94,8 @@ Conflicts: rootlesskit
 Replaces: rootlesskit
 Breaks: rootlesskit
 # slirp4netns (>= 0.4.0) is available in Debian since 11 and Ubuntu since 19.10
-Recommends: slirp4netns (>= 0.4.0)
-# Unlike RPM, DEB packages do not contain "Recommends: fuse-overlayfs (>= 0.7.0)" here,
-# because Debian (since 10) and Ubuntu support the kernel-mode rootless overlayfs.
+# fuse-overlayfs is recommended for Debian 10 and 11 (kernel < 5.11). Not needed for Ubuntu.
+Recommends: slirp4netns (>= 0.4.0~), ${fuse-overlayfs:Recommends}
 Description: Rootless support for Docker.
   Use dockerd-rootless.sh to run the daemon.
   Use dockerd-rootless-setuptool.sh to setup systemd for dockerd-rootless.sh .
diff --git a/deb/common/rules b/deb/common/rules
index 9b495e9..50a95da 100755
--- a/deb/common/rules
+++ b/deb/common/rules
@@ -3,6 +3,11 @@
 VERSION ?= $(shell cat engine/VERSION)
 TARGET_ARCH = $(shell dpkg-architecture -qDEB_TARGET_ARCH)
 
+override_dh_gencontrol:
+	# if we're not on Ubuntu, we need to Recommends: fuse-overlayfs in docker-ce-rootless-extras
+	echo 'fuse-overlayfs:Recommends=$(shell dpkg-vendor --is Ubuntu || echo 'fuse-overlayfs (>= 0.7.0~)')' >> debian/docker-ce-rootless-extras.substvars
+	dh_gencontrol
+
 # force packages to be built with xz compression, as Ubuntu 21.10 and up use
 # zstd compression, which is non-standard, and breaks 'dpkg-sig --verify'
 override_dh_builddeb:

(The trailing ~ on the version numbers allows them to be satisfied by backports if necessary too 👍)

[thaJeztah]

@AkihiroSuda could you have a look at Tianon's suggestion?

[AkihiroSuda]

@AkihiroSuda could you have a look at Tianon's suggestion?

Thanks, SGTM, but I haven't tested it

[AkihiroSuda]

Debian 12 is shipped with kernel 6.1, so I'm closing this