3 ms·

I don't think many people disagree that systemd implements some useful ideas. The problem is the overall architecture and the quality of the code.

geertj 9y ago
Some examples of poor quality of code? This has not been my experience. I've gone through the code base a couple of times for my own education and to do some small patches, and I found it clean and easy to read.
- zAy0LfpBZLC8mAC 9y ago
  The problem isn't so much "typical programming errors", but the appoach to solving problems. So, it's not that there are tons of buffer overflows in the code (well, not that I know of, though I didn't explicitly look for them either), but stuff such as the vulnerabilities in the DNS resolver because they reimplemented things from scratch without the necessary domain knowledge on how to do that securely that has been collected and implemented by the dozens of existing implementations over the decades, or the bug that caused .* to match .. and thus systems to be destroyed by the temp cleanup code, which is equally a potential pitfall that is well-documented and explicitly even standardized against in POSIX, but they still failed to implement this in a way that is both evidently sane and also otherwise generally accepted to be the correct way to do things ... and then they even pretended that it's somehow not actually a bug. Those are two somewhat recent examples I can think of, but there have been many more showing the same kind of attitude. They are ignoring hard-earned knowledge on how to do things securely, safely and reliably, they ignore the intentions of abstractions, and they pretend that obvious bugs aren't bugs because there is some weird way to reinterpret the bug into being correct behaviour (that noone expects and that causes harm).
  - deleted 9y ago
    [deleted]
  - someone12345 9y ago
    > stuff such as the vulnerabilities in the DNS resolver because they reimplemented things from scratch without the necessary domain knowledge on how to do that securely that has been collected and implemented by the dozens of existing implementations over the decades By domain knowledge how to do this securely in implementations tested oer time, do you mean something like https://access.redhat.com/articles/2161461 https://access.redhat.com/articles/2161461? It doesn't look like systemd's resolver fares worse in comparison... In addition it can be sandboxed (and is), an advantage over having a resolver part of libc.
    - zAy0LfpBZLC8mAC 9y ago
      Thank you for the demonstration, that is indeed roughly what that lack of domain knowledge combined with arrogance looks like. Would you mind explaining how exactly sandboxing prevents cache poisoning?
moreentropy 9y ago
I've had way more headache with badly written and plain faulty init scripts than with systemd, including systemd-networkd, systemd-timesyncd, systemd-resolved and systemd-nspawn, which I used to replace a lot of LXC, LXD and openvz setups.
- yupyup 9y ago
  Please, could you share a little of your experience with systemd-nspawn vs LXD? I have used LXD (with ZFS storage) in production but have not played with systemd-nspawn... Thanks!
  - moreentropy 9y ago
    Well it just works and is extremely simple to use. I usually debootstrap into /var/lib/machines/something and do "machinectl enable something; machinectl start something", that's it. Then I attach to the machine using "machienctl shell something" and configure networking (host0 interface) inside the domain, that's it. For drop in configuration systemd-nspawn parses a config file /etc/systemd/nspawn/something.nspawn which usually just contains network configuration on my hosts: [Network] Bridge=br-int Systemd-nspawn enables and user namespacing by default and chowns the machines's root filesystem on first start. If that's not desired (Things like Samba fileservers don't work well with user namespacing) just disable it in the .nspawn file: [Exec] PrivateUsers=no Everything you need to know is in the manpages systemd-nspawn and systemd.nspawn. I usually install systemd from stretch-backports because running a fairly recent systemd version helps as it still gets new features, but I never had problems with stability.
    - yupyup 9y ago
      Great, sounds quite simple. One thing I somewhat miss from what you are explaining is all the aditional things that LXD gets you (snapshots using ZFS, image publishing/sharing, migrating containers between LXD hosts...) But maybe some of those things are still doable (e.g. mounting a ZFS dataset as storage for /var/lib/machines/containerX)... Thanks for your answer!

geertj 9y ago

Some examples of poor quality of code? This has not been my experience. I've gone through the code base a couple of times for my own education and to do some small patches, and I found it clean and easy to read.

zAy0LfpBZLC8mAC 9y ago
The problem isn't so much "typical programming errors", but the appoach to solving problems. So, it's not that there are tons of buffer overflows in the code (well, not that I know of, though I didn't explicitly look for them either), but stuff such as the vulnerabilities in the DNS resolver because they reimplemented things from scratch without the necessary domain knowledge on how to do that securely that has been collected and implemented by the dozens of existing implementations over the decades, or the bug that caused .* to match .. and thus systems to be destroyed by the temp cleanup code, which is equally a potential pitfall that is well-documented and explicitly even standardized against in POSIX, but they still failed to implement this in a way that is both evidently sane and also otherwise generally accepted to be the correct way to do things ... and then they even pretended that it's somehow not actually a bug. Those are two somewhat recent examples I can think of, but there have been many more showing the same kind of attitude. They are ignoring hard-earned knowledge on how to do things securely, safely and reliably, they ignore the intentions of abstractions, and they pretend that obvious bugs aren't bugs because there is some weird way to reinterpret the bug into being correct behaviour (that noone expects and that causes harm).
- deleted 9y ago
  [deleted]
- someone12345 9y ago
  > stuff such as the vulnerabilities in the DNS resolver because they reimplemented things from scratch without the necessary domain knowledge on how to do that securely that has been collected and implemented by the dozens of existing implementations over the decades By domain knowledge how to do this securely in implementations tested oer time, do you mean something like https://access.redhat.com/articles/2161461 https://access.redhat.com/articles/2161461? It doesn't look like systemd's resolver fares worse in comparison... In addition it can be sandboxed (and is), an advantage over having a resolver part of libc.
  - zAy0LfpBZLC8mAC 9y ago
    Thank you for the demonstration, that is indeed roughly what that lack of domain knowledge combined with arrogance looks like. Would you mind explaining how exactly sandboxing prevents cache poisoning?

moreentropy 9y ago

I've had way more headache with badly written and plain faulty init scripts than with systemd, including systemd-networkd, systemd-timesyncd, systemd-resolved and systemd-nspawn, which I used to replace a lot of LXC, LXD and openvz setups.

yupyup 9y ago
Please, could you share a little of your experience with systemd-nspawn vs LXD? I have used LXD (with ZFS storage) in production but have not played with systemd-nspawn... Thanks!
- moreentropy 9y ago
  Well it just works and is extremely simple to use. I usually debootstrap into /var/lib/machines/something and do "machinectl enable something; machinectl start something", that's it. Then I attach to the machine using "machienctl shell something" and configure networking (host0 interface) inside the domain, that's it. For drop in configuration systemd-nspawn parses a config file /etc/systemd/nspawn/something.nspawn which usually just contains network configuration on my hosts: [Network] Bridge=br-int Systemd-nspawn enables and user namespacing by default and chowns the machines's root filesystem on first start. If that's not desired (Things like Samba fileservers don't work well with user namespacing) just disable it in the .nspawn file: [Exec] PrivateUsers=no Everything you need to know is in the manpages systemd-nspawn and systemd.nspawn. I usually install systemd from stretch-backports because running a fairly recent systemd version helps as it still gets new features, but I never had problems with stability.
  - yupyup 9y ago
    Great, sounds quite simple. One thing I somewhat miss from what you are explaining is all the aditional things that LXD gets you (snapshots using ZFS, image publishing/sharing, migrating containers between LXD hosts...) But maybe some of those things are still doable (e.g. mounting a ZFS dataset as storage for /var/lib/machines/containerX)... Thanks for your answer!