transmission-daemon: Couldn't save file "/tmp/transmission/settings.json": Resource busy (variant.c:1226)

[idarek]

<package-name>: transmission-daemon

OpenWrt 22.03.0 Askey RT4230W REV6 / RAC2V1K

Issue

Couldn't save file "/tmp/transmission/settings.json": Resource busy (variant.c:1226)

When starting daemon.

Removing procd-ujail from the system fixes it temporarily but when added torrent to download it crashes daemon and autostarts it on its own.

Hashing jail part from init script also result same issue of crashing daemon.

Removing package and reinstalling, enabling in config and starting /etc/init.d/transmission start result following in logread

daemon.err transmission-daemon[16422]: [2022-09-15 19:28:11.861] Couldn't save temporary file "/tmp/transmission/settings.json.tmp.XXXXXX": Permission denied (variant.c:1235)

Changing in settings user and group to root

        option user 'root'
        option group 'root'

result in

Thu Sep 15 19:30:00 2022 daemon.err transmission-daemon[16779]: [2022-09-15 19:30:00.803] Couldn't save file "/tmp/transmission/settings.json": Resource busy (variant.c:1226)

The only solution that still working is to comment jail and seccomp from transmission init file like described here

Temporary solution

#       seccomp_path="/etc/seccomp/transmission-daemon.json"
#       if [ -f "$seccomp_path" ]; then
#               procd_set_param seccomp "$seccomp_path"
#       fi

        if [ -z "$USE" ]; then
                procd_set_param limits core="0 0"
        else
                procd_set_param limits core="0 0" as="$USE $USE"
                logger -t transmission "Starting with $USE virt mem"
        fi

        [ -d "$web_home" ] && procd_set_param env TRANSMISSION_WEB_HOME="$web_home"
        [ "$ca_bundle" -gt 0 ] && procd_set_param env CURL_CA_BUNDLE="$ca_bundle_file"

#       procd_add_jail transmission log
#       procd_add_jail_mount "$config_file"
#       procd_add_jail_mount_rw "$config_dir/resume"
#       procd_add_jail_mount_rw "$config_dir/torrents"
#       procd_add_jail_mount_rw "$config_dir/blocklists"
#       procd_add_jail_mount_rw "$config_dir/stats.json"
#       procd_add_jail_mount_rw "$download_dir"
        web_home="${web_home:-/usr/share/transmission/web}"
#       [ -d "$web_home" ] && procd_add_jail_mount "$web_home"
#       [ -f "$ca_bundle_file" ] && procd_add_jail_mount "$ca_bundle_file"
        procd_close_instance
}

[neheb]

Yep. All this jail garbage has been causing issues since introduction. Maintainer is @dangowrt

[dangowrt]

The error message

daemon.err transmission-daemon[16422]: [2022-09-15 19:28:11.861] Couldn't save temporary file "/tmp/transmission/settings.json.tmp.XXXXXX": Permission denied (variant.c:1235)

should not prevent transmission from working (and it doesn't for me). It merely means that transmission could not make changes to it's the configuration, which on OpenWrt is generated by UCI and should be managed there. You shouldn't need to deactivate all procd-ujail based isolation to get transmission working. Which problems (apart from the log entry) do you observe? Do you see the transmission process running in ps output? Do you see it listening on control, dht and torrent ports in netstat -lnp output? If not, please share complete logread output.

@neheb If you prefer running transmission on your home device, potentially handling other sensitive data as well, only relying on a little bit of discrete UNIX access control, ok, go ahead and uninstall procd-ujail or comment-out the relevant parts of the transmission init script. Having it sit in it's own filesystem namespace, isolated from other processes and guarded by seccomp BPF filter definitely makes me feel a bit better, given that it's typically available for unsolicited TCP/UDP connections from the outside and/or uses UDP hole punching to communicate with random peers suggested by the DHT even if you don't give it an open port on a public address.

[neheb]

I don't run transmission.

Anyway, my point was that ever since its introduction to transmission, I've seen multiple people report issues.

[idarek]

Hi @dangowrt Yes, this issue doesn't prevent transmission from running. It causes all other issues like being unable to save settings (see settings.json file) or even saving files into the mounted drive (transmission returning that No space left).

Commending jail and seccomp do the trick and the app working as expected.

I admit I don't understand what procd_ujail and seccomp is in the first place. Tried to find the information about it, but there is not a lot with right explanation.

I don't think uninstalling procd_ujail and seccomp is a solution. For transmission commenting its use can be a solution, but for other critical processes if this is applied, then there is a reason for that.

I appreciate the creator of transmission looking on that or even the OpenWrt community (but I would not count on that, as the support is poor though that).

[dangowrt]

procd-ujail is a OpenWrt-specific way to isolate processes from the rest of the system using standard Linux Kernel interfaces designed for that purpose. In case of transmission it is used to hide unrelated filesystems away from it (using a filesystem namespace and bind mounts, ie. procd_add_jail_mount). In addition to that, seccomp is used to strictly limit the allowed interaction of the transmission process with the operating system (seccomp is like a firewall between an app and the OS).

Downloading files should work fine also with ujail. If you are trying to download into a directory other than the configured download_dir this won't work. As a hack, and to find out if this is the problem, add another procd_add_jail_mount_rw line to /etc/init.d/transmission for the directory you want to give transmission write access to. As many people seem to have the need to give transmission read-only or even read-write access to additional directories I will add UCI options in /etc/config/transmission for that purpose.

Regarding storing configuration: Letting transmission edit it's own configuration is intentionally not permitted as in OpenWrt the configuration is anyway generated again from what is in /etc/config/transmission on every restart. Temporary configuration changes, such as a temporary change of speed limits, do work despite the file not being written.

[idarek]

Thank you @dangowrt for explanation. Appreciated.

Will need to investigate why, despite, that though settings, the temporary directory shall have jail RW access, why is returning "Not enough disk space". There is something interesting happening here.

[jly77]

After moving download_dir to an external disk and set it correctly in config, error disappeared. Thanks @dangowrt

[alpha7504]

@jly77 hi Could you please explain how you solved this issue?

[geser2008]

Transmission can't also write "dht.dat" ans "stats.json" (even if I give them write permissions through "procd_add_jail_mount_rw"). Also "watch_dir" and "icompltete_dir" are not available and when I've activated them, transmission has stooped working. So I've modified /etc/init.d/transmission a little bit. Not sure if the result is completely correct and secure, but now it works without warnings and errors concerning file/folder permissions.

I've upload it here: https://pastebin.com/PDHUxqSU

[alpha7504]

Thanks for the response... I've checked that using your init.d file all the errors disappeared but this seems like a temporary solution. I wanna ask, how do I implement this in my own transmission init.d file?

[geser2008]

I've added this block (get variables for watch_dir from /etc/config/transmission)

local watch_dir
config_get watch_dir "$cfg" 'watch_dir' '/var/etc/transmission'
local watch_dir_enabled
config_get watch_dir_enabled "$cfg" 'watch_dir_enabled' 0

  and modified this one (give write permission to whole config_dir including all files/folders inside it, not to separate files/folders as it is in the original file)

procd_add_jail transmission log
procd_add_jail_mount_rw "$config_dir"
#procd_add_jail_mount "$config_file"
#procd_add_jail_mount_rw "$config_dir/resume"
#procd_add_jail_mount_rw "$config_dir/torrents"
#procd_add_jail_mount_rw "$config_dir/blocklists"
#procd_add_jail_mount_rw "$config_dir/stats.json"
procd_add_jail_mount_rw "$incomplete_dir"
procd_add_jail_mount_rw "$watch_dir"
procd_add_jail_mount_rw "$download_dir"

Modify yours /etc/init.d/transmission if you like.

[alpha7504]

Thank you

[Ulysses1960]

Thank you for this helpful informations. As I wanted to be able change the download location from the Web user interface for some kind of torrents, I had to add another line to my /etc/init.d/transmission file:

procd_add_jail_mount_rw /media/MyDisk/share/Music

The address must be hardcoded, so there is no flexibility for the user.

I would be thankful if these issues could be fixed for the 2023 release of OpenWrt/transmission.

[primoitt83]

hey guys..

I've installed transmission 3.00-18 on Openwrt 22.03.2 and my daemon wont work... looks like permission issue...

Here is my config briefly:

cat /etc/config/transmission
config transmission
    option enabled 1
    option config_dir '/etc/transmission'
    option config_overwrite '1'
    option user 'transmission'
    option group 'transmission'

Here is my workaround:

/etc/init.d/transmission stop
rm -Rf /etc/transmission
mkdir /etc/transmission
transmission-daemon -g /etc/transmission -f --log-debug

Waiting some minutes...then stop

cd /etc
chown transmission:224 transmission/ -R
chmod 775 transmission/ -R
/etc/init.d/transmission start

Now transmission-daemon goes up..

On logread still got this messages but transmission is working nicely

daemon.err transmission-daemon[2300]: [2023-01-28 07:53:59.535] Couldn't save temporary file "/etc/transmission/stats.json.tmp.XXXXXX": Permission denied (variant.c:1235)