Hacker News Reader

Comment by theandrewbailey | Hacker News Reader

In other words: integrate purge-old-kernels

http://manpages.ubuntu.com/manpages/xenial/man1/purge-old-ke...

Maybe add some stats to know which kernels have booted successfully, so one knows which old ones can be safely deleted, and keep the last 1 or 2 good ones (not always the latest!).

View on HN

$ apt-get install purge-old-kernels

    The program 'purge-old-kernels' is currently not installed.
    You can install it by typing: apt install byobu

"byobu"? packages.debian.org to the rescue...

https://packages.debian.org/jessie/byobu "Using Byobu, you can quickly create and move between different windows over a single SSH connection or TTY terminal, split each of those windows into multiple panes, monitor dozens of important statistics about your system, detach and reattach to sessions later while your programs continue to run in the background."

Uhm... what?

> "byobu"? packages.debian.org to the rescue...

You don't ned to use packages.debian.org to look up what packages do.

> apt show byobu .. Description: text window manager, shell multiplexer, integrated DevOps environment Byobu is Ubuntu's powerful text-based window manager, shell multiplexer, and integrated DevOps environment.

Quite right. One uses packages.ubuntu.com:

* http://packages.ubuntu.com/yakkety/all/byobu/filelist

(-:

byobu is basically an abstraction over screen and tmux, letting you use either with some common keybindings for spawning new windows and a common toolbar at the bottom telling you disk usage and load average and the like. I am not sure why purge-old-kernels is in the byobu package, that seems like a really poor placement for it.

It is a bad place for it. But it's there because I wrote both of them, and Byobu is always everywhere I want it to be, and I generally always want purge-old-kernels there too.

But yes, you're very right. It needs to be moved out.

Forgive the intrusion, just want to say thanks for Byobu. I use it regularly, and it's much nicer than bare tmux or screen.

:-) Thanks!

Are you sure you typed exactly that?

For `apt-get install purge-old-kernels` I get

    E: Could not open lock file /var/lib/dpkg/lock - open (13: Permission denied)
    E: Unable to lock the administration directory (/var/lib/dpkg/), are you root?

And for `sudo apt-get install purge-old-kernels`, I get

    Reading package lists... Done
    Building dependency tree       
    Reading state information... Done
    E: Unable to locate package purge-old-kernels

But I can reproduce your error by `purge-old-kernels` alone. That is indeed strange.

EDIT: I straced bash by `strace -o bashlog -f -s 10000 bash` and found the culprit to be /usr/lib/command-not-found. Indeed, if you run `/usr/lib/command-not-found -- purge-old-kernels` directly, you get that same message about byobu.

EDIT2: I assumed this was some kind of bug with the database, but now I actually tried installing byobu and it does make purge-old-kernels available.

The first of the two errors has nothing to do with the package itself - packages need root permisions to be managed, which is what exactly the error is telling you:

    E: Unable to lock the administration directory (/var/lib/dpkg/), are you root?
                                                                     ^^^^^^^^^^^^^

In your case, you didn't prepend `sudo`.

Regarding the second, which is instead the core of the problem, see the man page (http://manpages.ubuntu.com/manpages/xenial/man1/purge-old-ke...):

    Provided by: byobu_5.106-0ubuntu1_all bug

Therefore the correct (and full) command is:

    sudo apt-get install byobu

As pointed out in another comment, such package is arguably a poor placement for this type of utility.

I'm aware that the first errors don't have anything to do with the package itself, but this was the command line given. I was wondering what kind of setup might lead to an apt-get command (without sudo even) to display that error message.

One case (which may be irrelevant in this context, but still a valid scenario) is auto-updates being executed in the background.

So I'm the author of both Byobu and purge-old-kernels. It's in Debian, because I help push it there after I push it to Ubuntu.

It's completely wrong that purge-old-kernels is in Byobu, rather than in the kernel or directly handled by dpkg/apt. Thanks for all the feedback here -- we'll get that cleaned up in 17.10!

It shouldn't be needed. AFAIK part of the post-installation script of a new kernel already marks the oldest kernels for removal with `apt-get autoremove`. They just need to run it automatically after an upgrade.

Unfortunately, that's not enough. There are many corner cases where kernel packages hang around much longer than they should, for odd reasons.

Reply on news.ycombinator.com