This is the first step towards persistent VM data. For now, these directories are never reused, and also don't get cleaned up. Both are things to work on in future. Even without persistence, it's good to not have to store everything a VM might write into its home directory in RAM. For AppImage and Flatpak VMs, disk-backed directories are stored on the partition containing the AppImage or Flatpak, in the new Spectrum/ hierarchy. This will enable locating them for later reuse. System VMs, on the other hand, don't have a natural partition to store data on — there may not even be a writable partition at the time they're launched. Since we don't expect persistence from system VMs, we just use a tmpfs for their "disk-backed" directories, which is reset on every boot. Doing it this way avoids the need for multiple routes in img/app — it can always assume it gets a "disk" directory from the host. For manually imported VMs, it's up to the user where these directories should be, or whether they should have the same behavior as system VMs. Signed-off-by: Alyssa Ross <hi@alyssa.is> --- v2: reset "disk-backed" directories of system VMs between boots v1: https://spectrum-os.org/lists/archives/spectrum-devel/20251213161637.510752-... .../using-spectrum/creating-custom-vms.adoc | 10 ++++-- .../image/usr/bin/create-vm-dependencies | 1 + host/rootfs/image/usr/bin/run-appimage | 22 ++++++++++--- host/rootfs/image/usr/bin/run-flatpak | 15 ++++++++- host/rootfs/image/usr/bin/run-vmm | 32 ++++++++++++++++++- host/rootfs/image/usr/bin/vm-import | 17 +++++++++- img/app/Makefile | 2 +- img/app/image/etc/fstab | 1 - img/app/image/etc/s6-rc/app/run | 7 ++-- img/app/scripts/start-virtiofsd.elb | 2 +- release/checks/integration/lib.c | 3 +- release/checks/integration/networking.c | 2 +- release/checks/integration/portal.c | 2 +- 13 files changed, 97 insertions(+), 19 deletions(-) diff --git a/Documentation/using-spectrum/creating-custom-vms.adoc b/Documentation/using-spectrum/creating-custom-vms.adoc index 229c0140..68213c89 100644 --- a/Documentation/using-spectrum/creating-custom-vms.adoc +++ b/Documentation/using-spectrum/creating-custom-vms.adoc @@ -13,9 +13,13 @@ configurations are directories under a dedicated parent directory, and the name of each configuration directory determines the name of the VM. After mounting the persistent storage partition, the configured VMs can be made available by running `vm-import user -/media/4e43cdc2-82b2-4d94-8a90-b6c6189312d2/vms`, replacing -/media/4e43cdc2-82b2-4d94-8a90-b6c6189312d2/vms with the directory -containing the VM definitions. +/media/4e43cdc2-82b2-4d94-8a90-b6c6189312d2/vms +/media/4e43cdc2-82b2-4d94-8a90-b6c6189312d2/Spectrum/data/spectrum/storage`, +replacing /media/4e43cdc2-82b2-4d94-8a90-b6c6189312d2/vms with the +directory containing the VM definitions, and +/media/4e43cdc2-82b2-4d94-8a90-b6c6189312d2/Spectrum/data/spectrum/storage +with the directory where disk-backed directories for the VMs should be +created. The directory can contain the following files: diff --git a/host/rootfs/image/usr/bin/create-vm-dependencies b/host/rootfs/image/usr/bin/create-vm-dependencies index 6bf12d03..b7545425 100755 --- a/host/rootfs/image/usr/bin/create-vm-dependencies +++ b/host/rootfs/image/usr/bin/create-vm-dependencies @@ -6,6 +6,7 @@ if { mkdir -p /run/doc/${1}/doc /run/fs/${1}/config + /run/fs/${1}/disk /run/fs/${1}/doc /run/vm/by-id/${1}/ns } diff --git a/host/rootfs/image/usr/bin/run-appimage b/host/rootfs/image/usr/bin/run-appimage index b9464f8b..f62844f8 100755 --- a/host/rootfs/image/usr/bin/run-appimage +++ b/host/rootfs/image/usr/bin/run-appimage @@ -25,6 +25,18 @@ if { if { create-vm-dependencies $id } } +backtick diskdir { + s6-setuidgid fs + + backtick -E mountpoint { + importas -Siu 1 + findmnt -no TARGET -T $1 + } + + if { mkdir -p -- ${mountpoint}/Spectrum/data/spectrum/storage } + mktemp -d -- ${mountpoint}/Spectrum/data/spectrum/storage/tmp.XXXXXX +} + if { s6-envuidgid fs s6-applyuidgid -Uzu 0 @@ -32,15 +44,17 @@ if { multisubstitute { importas -Siu id importas -Siu 1 + importas -Siu diskdir } nsenter --preserve-credentials -S0 --mount=/run/vm/by-id/${id}/ns/mnt --user=/run/vm/by-id/${id}/ns/user - cd /run/fs/${id}/config - if { redirfd -w 1 type echo appimage } - if { touch run } - mount --bind $1 run + cd /run/fs/${id} + if { redirfd -w 1 config/type echo appimage } + if { touch config/run } + if { mount --bind $1 config/run } + mount --bind -- $diskdir disk } importas -Siu id diff --git a/host/rootfs/image/usr/bin/run-flatpak b/host/rootfs/image/usr/bin/run-flatpak index 2d3e7ea0..9a7ffa33 100755 --- a/host/rootfs/image/usr/bin/run-flatpak +++ b/host/rootfs/image/usr/bin/run-flatpak @@ -25,21 +25,34 @@ if { if { create-vm-dependencies $id } } +backtick diskdir { + s6-setuidgid fs + + importas -Siu 1 + + if { mkdir -p -- ${1}/Spectrum/data/spectrum/storage } + mktemp -d -- ${1}/Spectrum/data/spectrum/storage/tmp.XXXXXX +} + if { s6-envuidgid fs s6-applyuidgid -Uzu 0 multisubstitute { importas -Siu id + importas -Siu diskdir elgetpositionals } nsenter --preserve-credentials -S0 --mount=/run/vm/by-id/${id}/ns/mnt --user=/run/vm/by-id/${id}/ns/user + cd /run/fs/${id}/config if { redirfd -w 1 type echo flatpak } - mount-flatpak $@ + if { mount-flatpak $@ } + + mount --bind -- $diskdir /run/fs/${id}/disk } importas -Siu id diff --git a/host/rootfs/image/usr/bin/run-vmm b/host/rootfs/image/usr/bin/run-vmm index 7c2b9af5..4661f5f5 100755 --- a/host/rootfs/image/usr/bin/run-vmm +++ b/host/rootfs/image/usr/bin/run-vmm @@ -1,7 +1,37 @@ -#!/bin/execlineb -s0 +#!/bin/execlineb # SPDX-License-Identifier: EUPL-1.2+ # SPDX-FileCopyrightText: 2024-2025 Alyssa Ross <hi@alyssa.is> +if { + backtick -D "" mnt { + importas -Siu 1 + nsenter --mount=/run/vm/by-id/${1}/ns/mnt + findmnt -no FSTYPE,SOURCE /run/fs/${1}/disk + } + + multisubstitute { + importas -Siu mnt + importas -Siu 1 + } + + case $mnt { + "^$|^tmpfs fallback$" { + s6-envuidgid fs + s6-applyuidgid -Uzu 0 + nsenter --preserve-credentials -S0 + --mount=/run/vm/by-id/${1}/ns/mnt + --user=/run/vm/by-id/${1}/ns/user + foreground { + redirfd -w 2 /dev/null + umount -- /run/fs/${1}/disk + } + mount -t tmpfs -o mode=0700 -- fallback /run/fs/${1}/disk + } + } +} + +elgetpositionals + s6-ipcserver-socketbinder -B /run/vm/by-id/${1}/vmm getpid -E vmm_pid diff --git a/host/rootfs/image/usr/bin/vm-import b/host/rootfs/image/usr/bin/vm-import index 014eab87..e931ddd7 100755 --- a/host/rootfs/image/usr/bin/vm-import +++ b/host/rootfs/image/usr/bin/vm-import @@ -1,4 +1,4 @@ -#!/bin/execlineb -S2 +#!/bin/execlineb -S3 # SPDX-License-Identifier: EUPL-1.2+ # SPDX-FileCopyrightText: 2023-2024 Alyssa Ross <hi@alyssa.is> @@ -20,4 +20,19 @@ if { ln -s -- /run/service/vmm/instance/${id} /run/vm/by-id/${id}/service } if { create-vm-dependencies $id } +if { + case $# { + 3 { + s6-envuidgid fs + s6-applyuidgid -Uzu 0 + nsenter --preserve-credentials -S0 + --mount=/run/vm/by-id/${id}/ns/mnt + --user=/run/vm/by-id/${id}/ns/user + + if { mkdir -p -- ${3}/${name} } + mount --bind -- ${3}/${name} /run/fs/${id}/disk + } + } +} + s6-instance-create -- /run/service/vmm $id diff --git a/img/app/Makefile b/img/app/Makefile index 7e3d05b2..2e720a91 100644 --- a/img/app/Makefile +++ b/img/app/Makefile @@ -30,7 +30,7 @@ $(imgdir)/appvm/blk/root.img: ../../scripts/make-gpt.sh ../../scripts/sfdisk-fie build/rootfs.erofs:root:5460386f-2203-4911-8694-91400125c604:root mv $@.tmp $@ -DIRS = dev home/user host run mnt proc sys tmp \ +DIRS = dev host run mnt proc sys tmp \ etc/s6-linux-init/run-image/pipewire \ etc/s6-linux-init/run-image/service \ etc/s6-linux-init/run-image/user \ diff --git a/img/app/image/etc/fstab b/img/app/image/etc/fstab index 5f78ab87..f51eace0 100644 --- a/img/app/image/etc/fstab +++ b/img/app/image/etc/fstab @@ -5,4 +5,3 @@ devpts /dev/pts devpts nosuid,noexec,gid=5,mode=620 0 0 tmpfs /dev/shm tmpfs nosuid,nodev 0 0 sysfs /sys sysfs nosuid,nodev,noexec 0 0 tmpfs /tmp tmpfs nosuid,nodev 0 0 -tmpfs /home/user tmpfs nodev,mode=0700,uid=1000,gid=1000 0 0 diff --git a/img/app/image/etc/s6-rc/app/run b/img/app/image/etc/s6-rc/app/run index f91877d4..f36d153c 100755 --- a/img/app/image/etc/s6-rc/app/run +++ b/img/app/image/etc/s6-rc/app/run @@ -4,11 +4,12 @@ export TMPDIR /run -export HOME /home/user -cd /home/user - if { /etc/mdev/wait virtiofs-host } +if { install -do user -g user /host/disk/home } +export HOME /host/disk/home +cd /host/disk/home + foreground { redirfd -r 0 /host/config/type withstdinas -E type diff --git a/img/app/scripts/start-virtiofsd.elb b/img/app/scripts/start-virtiofsd.elb index 9efb436b..d861a22b 100755 --- a/img/app/scripts/start-virtiofsd.elb +++ b/img/app/scripts/start-virtiofsd.elb @@ -7,7 +7,7 @@ background { if { mkdir -p build/fs } unshare -rUm if { mount -t tmpfs -o nosuid,nodev fs build/fs } - if { mkdir build/fs/config } + if { mkdir build/fs/config build/fs/disk } if { importas -Si CONFIG mount --rbind -- ${CONFIG}/fs build/fs/config } unshare --map-user 1000 --map-group 1000 importas -SsD virtiofsd VIRTIOFSD diff --git a/release/checks/integration/lib.c b/release/checks/integration/lib.c index 51f6bae7..3dcce471 100644 --- a/release/checks/integration/lib.c +++ b/release/checks/integration/lib.c @@ -195,6 +195,7 @@ struct vm *start_qemu(struct config c) "-drive", nullptr, "-drive", nullptr, "-smbios", nullptr, + "-snapshot", "-m", "4G", "-nodefaults", "-machine", "virtualization=on", @@ -242,7 +243,7 @@ struct vm *start_qemu(struct config c) if (asprintf(efi_arg, "file=%s,format=raw,if=pflash,readonly=true", c.drives.efi) == -1 || asprintf(img_arg, "file=%s,format=raw,if=virtio,readonly=true", c.drives.img) == -1 || - asprintf(user_data_arg, "file=%s,format=raw,if=virtio,readonly=true", c.drives.user_data) == -1 || + asprintf(user_data_arg, "file=%s,format=raw,if=virtio", c.drives.user_data) == -1 || asprintf(console_arg, "type=11,value=io.systemd.stub.kernel-cmdline-extra=%s%s", c.serial.console ? "console=" : "", c.serial.console ? c.serial.console : "") == -1) { diff --git a/release/checks/integration/networking.c b/release/checks/integration/networking.c index 078e31fc..d581b647 100644 --- a/release/checks/integration/networking.c +++ b/release/checks/integration/networking.c @@ -151,7 +151,7 @@ void test(struct config c) "mkdir /run/mnt && " "mount \"$(findfs UUID=a7834806-2f82-4faf-8ac4-4f8fd8a474ca)\" /run/mnt && " "s6-rc -bu change vmm-env && " - "vm-import user /run/mnt/vms && " + "vm-import user /run/mnt/vms /run/mnt/storage && " "vm-start \"$(basename \"$(readlink /run/vm/by-name/user.nc)\")\" && " "tail -Fc +0 /run/log/current /run/*.log &\n", vm_console_writer(vm)) == EOF) { diff --git a/release/checks/integration/portal.c b/release/checks/integration/portal.c index 6ba5654a..dc459791 100644 --- a/release/checks/integration/portal.c +++ b/release/checks/integration/portal.c @@ -16,7 +16,7 @@ void test(struct config c) "mkdir /run/mnt && " "mount \"$(findfs UUID=a7834806-2f82-4faf-8ac4-4f8fd8a474ca)\" /run/mnt && " "s6-rc -bu change vmm-env && " - "vm-import user /run/mnt/vms && " + "vm-import user /run/mnt/vms /run/mnt/storage && " "(tail -Fc +0 /run/*.log &) && " "s6-svc -O /run/vm/by-name/user.portal/service && " "vm-start \"$(basename \"$(readlink /run/vm/by-name/user.portal)\")\" && " -- 2.51.0

Signed-off-by: Alyssa Ross <hi@alyssa.is> --- v2: no change host/rootfs/image/usr/bin/run-appimage | 7 +++++-- host/rootfs/image/usr/bin/run-flatpak | 7 +++++-- 2 files changed, 10 insertions(+), 4 deletions(-) diff --git a/host/rootfs/image/usr/bin/run-appimage b/host/rootfs/image/usr/bin/run-appimage index f62844f8..de851c52 100755 --- a/host/rootfs/image/usr/bin/run-appimage +++ b/host/rootfs/image/usr/bin/run-appimage @@ -57,7 +57,10 @@ if { mount --bind -- $diskdir disk } -importas -Siu id +multisubstitute { + importas -Siu diskdir + importas -Siu id +} piperw 4 3 background { @@ -76,4 +79,4 @@ fdclose 3 if { s6-instance-delete /run/service/vm-services $id } if { umount -R /run/vm/by-id/${id}/ns } -rm -r /run/vm/by-id/${id} /run/configs/${id} +rm -r -- $diskdir /run/vm/by-id/${id} /run/configs/${id} diff --git a/host/rootfs/image/usr/bin/run-flatpak b/host/rootfs/image/usr/bin/run-flatpak index 9a7ffa33..b47204c9 100755 --- a/host/rootfs/image/usr/bin/run-flatpak +++ b/host/rootfs/image/usr/bin/run-flatpak @@ -55,7 +55,10 @@ if { mount --bind -- $diskdir /run/fs/${id}/disk } -importas -Siu id +multisubstitute { + importas -Siu diskdir + importas -Siu id +} if { piperw 4 3 @@ -75,4 +78,4 @@ if { if { s6-instance-delete -- /run/service/vm-services $id } if { umount -R /run/vm/by-id/${id}/ns } -rm -r /run/vm/by-id/${id} /run/configs/${id} +rm -r -- $diskdir /run/vm/by-id/${id} /run/configs/${id} -- 2.51.0

In the ideal case, these will be cleaned up when the VM running them exits, but there's always the possibility that there are some left over, in which case mount time is the perfect time to clean up, when we can be reasonably sure nothing else is still accessing them. Signed-off-by: Alyssa Ross <hi@alyssa.is> --- v2: no change, but thanks to rebase no longer fails to exit after outputting error message as identified last time. v1: https://spectrum-os.org/lists/archives/spectrum-devel/20251213161637.510752-... host/rootfs/image/usr/bin/mount-userdata | 42 ++++++++++++++++-------- 1 file changed, 28 insertions(+), 14 deletions(-) diff --git a/host/rootfs/image/usr/bin/mount-userdata b/host/rootfs/image/usr/bin/mount-userdata index 71f12c55..4b9dc8a1 100755 --- a/host/rootfs/image/usr/bin/mount-userdata +++ b/host/rootfs/image/usr/bin/mount-userdata @@ -7,21 +7,35 @@ backtick -D "" uuid { blkid -o value -s UUID -- $1 } -multisubstitute { - importas -Siu 0 - importas -Siu 1 - importas -Siu uuid -} - -case $uuid { - "" { - if { - fdmove -c 1 2 - printf "%s: '%s' does not have a UUID\n" $0 $1 - } - exit 1 +if { + multisubstitute { + importas -Siu 0 + importas -Siu 1 + importas -Siu uuid } + + case $uuid { + "" { + if { + fdmove -c 1 2 + printf "%s: '%s' does not have a UUID\n" $0 $1 + } + exit 1 + } + } + + mount -m -t btrfs -o nosuid,nodev,noexec,nosymfollow -- $1 /media/${uuid} +} + +importas -Siu uuid + +foreground { + if -t { test -d /media/${uuid}/Spectrum/data/spectrum/storage } + find /media/${uuid}/Spectrum/data/spectrum/storage + -mindepth 1 + -maxdepth 1 + -name tmp.* + -exec rm -rf -- {} ; } -if { mount -m -t btrfs -o nosuid,nodev,noexec,nosymfollow -- $1 /media/${uuid} } printf "%s\n" /media/${uuid} -- 2.51.0

This allows the disk-backed directory of a running VM to be made persistent, with a user-provided name. This is done by renaming the directory to have a "persist." prefix rather than the "tmp." one the cleaner will look for. Since the VM's virtiofsd accesses the directory via a bind mount, this rename will be unnoticeable to the guest. musl has quite a bit of catching up to do with the APIs used here, which requires the use of a lot of raw syscalls. This even applies to some syscalls musl has wrappers for, like mkdirat(2), because musl's mkdirat() comes from <sys/stat.h>, which defines a struct statx that's missing the stx_mnt_id member we need. There doesn't even seem to be a SYS_statmount, so we use __NR_ constants throughout for consistency. Signed-off-by: Alyssa Ross <hi@alyssa.is> --- v2: new this round tools/default.nix | 1 + tools/meson.build | 4 + tools/vm-set-persist.c | 179 +++++++++++++++++++++++++++++++++++++++++ 3 files changed, 184 insertions(+) create mode 100644 tools/vm-set-persist.c diff --git a/tools/default.nix b/tools/default.nix index 56f41cd9..f094594f 100644 --- a/tools/default.nix +++ b/tools/default.nix @@ -78,6 +78,7 @@ stdenv.mkDerivation (finalAttrs: { ./start-vmm ./subprojects ./updates-dir-check.c + ./vm-set-persist.c ] ++ lib.optionals driverSupport [ ./xdp-forwarder ])); diff --git a/tools/meson.build b/tools/meson.build index 666483b3..06aa24d7 100644 --- a/tools/meson.build +++ b/tools/meson.build @@ -37,6 +37,10 @@ if get_option('host') executable('updates-dir-check', 'updates-dir-check.c', c_args : '-D_GNU_SOURCE', install: true) + + executable('vm-set-persist', 'vm-set-persist.c', + c_args : '-D_GNU_SOURCE', + install: true) endif if get_option('build') diff --git a/tools/vm-set-persist.c b/tools/vm-set-persist.c new file mode 100644 index 00000000..ac759504 --- /dev/null +++ b/tools/vm-set-persist.c @@ -0,0 +1,179 @@ +// SPDX-FileCopyrightText: 2025 Alyssa Ross <hi@alyssa.is> +// SPDX-License-Identifier: EUPL-1.2+ + +#include <err.h> +#include <fcntl.h> +#include <libgen.h> +#include <unistd.h> +#include <sched.h> +#include <stdio.h> +#include <stdlib.h> +#include <stdint.h> +#include <string.h> + +// No <sys/stat.h> until musl declares stx_mnt_id. +#include <sys/syscall.h> + +#include <linux/fs.h> +#include <linux/mount.h> +#include <linux/openat2.h> +#include <linux/stat.h> +#include <linux/unistd.h> + +// Including trailing NUL bytes. +static const int MNT_ROOT_MAX_LEN = 43; +static const int SOURCE_MAX_LEN = 28; + +static void set_mount_namespace(const char vm_id[static 1]) +{ + char ns_path[28]; + int r = snprintf(ns_path, sizeof ns_path, + "/run/vm/by-id/%s/ns/mnt", vm_id); + + if (r == -1) + err(EXIT_FAILURE, "snprintf"); + if ((size_t)r >= sizeof ns_path) + errx(EXIT_FAILURE, "VM ID unexpectedly long"); + + if ((r = open(ns_path, O_RDONLY | O_CLOEXEC)) == -1) + err(EXIT_FAILURE, "open"); + if (setns(r, CLONE_NEWNS) == -1) + err(EXIT_FAILURE, "setns"); + close(r); +} + +static void do_statx(const char path[static 1], + mode_t mode[static 1], uint64_t mnt_id[static 1]) +{ + struct statx stx; + + if (syscall(__NR_statx, AT_FDCWD, path, AT_SYMLINK_NOFOLLOW, + STATX_MODE | STATX_MNT_ID_UNIQUE, &stx) == -1) + err(EXIT_FAILURE, "statx"); + + if (!(stx.stx_attributes & STATX_ATTR_MOUNT_ROOT)) { + if (stx.stx_attributes_mask & STATX_ATTR_MOUNT_ROOT) + errx(EXIT_FAILURE, + "VM disk-backed directory not mounted"); + + errx(EXIT_FAILURE, "statx didn't return STATX_ATTR_MOUNT_ROOT"); + } + + if (!(stx.stx_mask & STATX_MNT_ID_UNIQUE)) + errx(EXIT_FAILURE, "statx didn't return STATX_MNT_ID_UNIQUE"); + if (!(stx.stx_mask & STATX_MODE)) + errx(EXIT_FAILURE, "statx didn't return STATX_MODE"); + + *mode = stx.stx_mode; + *mnt_id = stx.stx_mnt_id; +} + +static int do_mount(const char source[static 1]) +{ + int mnt, fs = syscall(__NR_fsopen, "btrfs", FSOPEN_CLOEXEC); + if (fs == -1) + err(EXIT_FAILURE, "fsopen"); + if (syscall(__NR_fsconfig, fs, FSCONFIG_SET_STRING, + "source", source, 0) == -1) + err(EXIT_FAILURE, "FSCONFIG_SET_STRING source"); + if (syscall(__NR_fsconfig, fs, FSCONFIG_SET_FLAG, + "rw", nullptr, 0) == -1) + err(EXIT_FAILURE, "FSCONFIG_SET_FLAG rw"); + if (syscall(__NR_fsconfig, fs, FSCONFIG_CMD_CREATE, + nullptr, nullptr, 0) == -1) + err(EXIT_FAILURE, "FSCONFIG_CMD_CREATE"); + if ((mnt = syscall(__NR_fsmount, fs, FSMOUNT_CLOEXEC, + MOUNT_ATTR_NOSUID | MOUNT_ATTR_NOSYMFOLLOW | + MOUNT_ATTR_NOEXEC | MOUNT_ATTR_NODEV)) == -1) + err(EXIT_FAILURE, "fsmount"); + close(fs); + return mnt; +} + +static void do_statmount(uint64_t mnt_id, + char mnt_root[static MNT_ROOT_MAX_LEN], + char source[static SOURCE_MAX_LEN]) +{ + int r; + char sm_buf[sizeof(struct statmount) + + MNT_ROOT_MAX_LEN + SOURCE_MAX_LEN]; + struct statmount *sm = (struct statmount *)sm_buf; + struct mnt_id_req req = { + .size = sizeof req, + .mnt_id = mnt_id, + .param = STATMOUNT_MNT_ROOT | STATMOUNT_SB_SOURCE, + }; + + if (syscall(__NR_statmount, &req, sm, sizeof sm_buf, 0) == -1) + err(EXIT_FAILURE, "statmount"); + + r = snprintf(mnt_root, MNT_ROOT_MAX_LEN, "%s", sm->str + sm->mnt_root); + if (r == -1) + err(EXIT_FAILURE, "snprintf"); + if (r >= MNT_ROOT_MAX_LEN) + errx(EXIT_FAILURE, "unexpectedly long mnt_root"); + + r = snprintf(source, SOURCE_MAX_LEN, "%s", sm->str + sm->sb_source); + if (r == -1) + err(EXIT_FAILURE, "snprintf"); + if (r >= SOURCE_MAX_LEN) + errx(EXIT_FAILURE, "unexpectedly long sb_source"); +} + +static void do_rename(int mnt, const char dir_name[static 1], + const char old_name[static 1], + const char new_name[static 1], mode_t mode) +{ + struct open_how how = { + .flags = O_PATH | O_CLOEXEC | O_DIRECTORY | O_NOFOLLOW, + .resolve = RESOLVE_NO_MAGICLINKS | RESOLVE_IN_ROOT | + RESOLVE_NO_SYMLINKS | RESOLVE_NO_XDEV, + }; + int dir = syscall(__NR_openat2, mnt, dir_name, &how, sizeof how); + if (dir == -1) + err(EXIT_FAILURE, "openat2"); + + if (syscall(__NR_mkdirat, dir, new_name, mode) == -1) + err(EXIT_FAILURE, "mkdirat"); + if (syscall(__NR_renameat2, dir, old_name, dir, new_name, + RENAME_EXCHANGE) == -1) + err(EXIT_FAILURE, "renameat2"); +} + +int main(int argc, char *argv[]) +{ + int mnt; + mode_t mode; + uint64_t mnt_id; + char *disk_path, *dir_name, *old_name, *new_name, + mnt_root[MNT_ROOT_MAX_LEN], source[SOURCE_MAX_LEN]; + + if (argc != 3) { + fprintf(stderr, "Usage: vm-set-persist ID INSTANCE\n"); + exit(EXIT_FAILURE); + } + + if (strchr(argv[1], '/')) + errx(EXIT_FAILURE, "invalid VM ID"); + if (strchr(argv[2], '/')) + errx(EXIT_FAILURE, "invalid persistent directory name"); + + if (asprintf(&disk_path, "/run/fs/%s/disk", argv[1]) == -1) + err(EXIT_FAILURE, "asprintf"); + if (asprintf(&new_name, "persist.%s", argv[2]) == -1) + err(EXIT_FAILURE, "asprintf"); + + set_mount_namespace(argv[1]); + + do_statx(disk_path, &mode, &mnt_id); + do_statmount(mnt_id, mnt_root, source); + + if (!(dir_name = strdup(mnt_root))) + err(EXIT_FAILURE, "strdup"); + dir_name = dirname(dir_name); + old_name = basename(mnt_root); + + mnt = do_mount(source); + + do_rename(mnt, dir_name, old_name, new_name, mode); +} -- 2.51.0

This allows run-appimage and run-flatpak to be given the name of a previously saved persistent directory. Further writes by the application to that directory will also be persisted. Signed-off-by: Alyssa Ross <hi@alyssa.is> --- v2: new this round host/rootfs/image/usr/bin/run-appimage | 16 +++++++++++++--- host/rootfs/image/usr/bin/run-flatpak | 15 +++++++++++++-- 2 files changed, 26 insertions(+), 5 deletions(-) diff --git a/host/rootfs/image/usr/bin/run-appimage b/host/rootfs/image/usr/bin/run-appimage index de851c52..24621065 100755 --- a/host/rootfs/image/usr/bin/run-appimage +++ b/host/rootfs/image/usr/bin/run-appimage @@ -26,13 +26,23 @@ if { } backtick diskdir { - s6-setuidgid fs - - backtick -E mountpoint { + backtick mountpoint { importas -Siu 1 findmnt -no TARGET -T $1 } + if -tn { + redirfd -w 2 /dev/null + multisubstitute { + importas -Siu mountpoint + importas -Siu 2 + } + printf "%s/Spectrum/data/spectrum/storage/persist.%s\n" $mountpoint $2 + } + + s6-setuidgid fs + + importas -Siu mountpoint if { mkdir -p -- ${mountpoint}/Spectrum/data/spectrum/storage } mktemp -d -- ${mountpoint}/Spectrum/data/spectrum/storage/tmp.XXXXXX } diff --git a/host/rootfs/image/usr/bin/run-flatpak b/host/rootfs/image/usr/bin/run-flatpak index b47204c9..4123d329 100755 --- a/host/rootfs/image/usr/bin/run-flatpak +++ b/host/rootfs/image/usr/bin/run-flatpak @@ -26,6 +26,15 @@ if { } backtick diskdir { + if -tn { + redirfd -w 2 /dev/null + multisubstitute { + importas -Siu 1 + importas -Siu 4 + } + printf "%s/Spectrum/data/spectrum/storage/persist.%s\n" $1 $4 + } + s6-setuidgid fs importas -Siu 1 @@ -41,7 +50,9 @@ if { multisubstitute { importas -Siu id importas -Siu diskdir - elgetpositionals + importas -Siu 1 + importas -Siu 2 + importas -Siu 3 } nsenter --preserve-credentials -S0 @@ -50,7 +61,7 @@ if { cd /run/fs/${id}/config if { redirfd -w 1 type echo flatpak } - if { mount-flatpak $@ } + if { mount-flatpak $1 $2 $3 } mount --bind -- $diskdir /run/fs/${id}/disk } -- 2.51.0

Signed-off-by: Alyssa Ross <hi@alyssa.is> --- v2: new this round .../using-spectrum/vm-file-access.adoc | 33 +++++++++++++++++-- 1 file changed, 30 insertions(+), 3 deletions(-) diff --git a/Documentation/using-spectrum/vm-file-access.adoc b/Documentation/using-spectrum/vm-file-access.adoc index 1546d57d..6189233f 100644 --- a/Documentation/using-spectrum/vm-file-access.adoc +++ b/Documentation/using-spectrum/vm-file-access.adoc @@ -2,11 +2,38 @@ :page-parent: Using Spectrum :page-nav_order: 1 -// SPDX-FileCopyrightText: 2024 Alyssa Ross <hi@alyssa.is> +// SPDX-FileCopyrightText: 2024-2025 Alyssa Ross <hi@alyssa.is> // SPDX-License-Identifier: GFDL-1.3-no-invariants-or-later OR CC-BY-SA-4.0 -Spectrum VMs start without any access to user data, but the user can -grant VMs access to files while the VM is running. +Spectrum VMs start without any access to user data, and with all +application state being discarded when the VM exits, but these +restrictions can be softened at runtime as required. + +== Persistent application data + +To make an application VM persistent, run, for example, +`vm-set-persist gGKghi configured`, where "gGKghi" is the VM's ID (can +be found using xref:running-vms.adoc#basic-vm-commands[`lsvm`]) and +"configured" is the name to be given to this persistent application +instance. The VM's home directory will now be saved under the given +name. For now, names are scoped to only to a user data partition, not +to an application, so you cannot create instances of different +applications with the same name. + +Then, to start a VM with that persistent data in future, give the +instance name to `run-appimage` or `run-flatpak` as an extra argument. +This run of the application will also persist further changes to its +home directory under the same name. + +Persistent application data is stored as directories prefixed with +"persist." under Spectrum/data/spectrum/storage on the user data +partition. They can be manually renamed, and, as long as they are not +being used by a currently running VM, removed. + +For manually configured VMs, persistence can optionally be enabled +when the VM is imported, by providing the storage location as an extra +argument to `vm-import`. The name of each imported VM will be used as +its instance name. == File chooser portal -- 2.51.0