Episode: 1167
Title: HPR1167: Kernels in the Boot, or What to Do When Your /boot folder Fills Up
Source: https://hub.hackerpublicradio.org/ccdn.php?filename=/eps/hpr1167/hpr1167.mp3
Transcribed: 2025-10-17 20:52:50

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Howdy folks, this is 5150 for Hacker Public Radio.
I thought you might find it instructive for this episode if I hold you about a problem
I had with my home server a week or so back and what I did to solve it.
You may have heard me mention that I purchased a used rack server a couple years ago to help
teach myself Linux server administration.
It's an old HP DL-38G3 with dual single core z-ons and 12 giga RAM, in other words it's
a P4 ear system.
It came with 275 gigs of Guzzi drives in Rade 1, which I dedicated to the OS.
It's a seller wanted more for additional internal Guzzi drives and those old server drives
are limited to only 120 gigabyte anyway.
I plugged in a PCIX SATA adapter and connected a 750 gig drive externally and mounted it
as my slash home.
I moved the 2 gigabyte USB drive that it had on my Chumby or to the server as opposed
to transferring the files or I don't think I had enough room on the 750 gig drive anyway
and it shows up under slash media slash USB 0.
I installed Linux server 10.04 recently updated 12.04 and you may wonder why I'd used
Ubuntu server but I found out CINOS which I wanted to install didn't support the Rade
controller out of the box.
You could install the right packages and make it work but I just took the easy way out
and I'd been frustrated at that time by DeFi and Lini on lack of support for up to date
packages on the desktop and I really didn't want to repeat that with my server.
So with 75 gigabytes dedicated to just the OS and application packages you can imagine
my surprise when after an update and upgrade I had a report that my slash boot was full.
It was until I looked at the output from FDES that I remembered that the Ubuntu installer
created a separate partition for slash boot.
At the risk of oversimplifying the purpose of slash boot it is where your current and
past kernel files are stored as well as configuration for grip.
Unless the system removes older kernels as most desktop systems seem to the storage
required slash boot will increase with every kernel upgrade and if you're following
along on the show notes I've included my output in the DF file before calling the kernel
and the one you're looking at is third one from the bottom.
That's slash dev slash CCISS slash C0D0P1 so that's the first partition on the hardware
rate array and you see that's dedicated to slash boot or mounted on slash boot and I
have 100% full zero free space available and then below that in the show notes I've included
directory listing of files that are in slash boot and if you just read down through
the numbers you can see I've got every kernel in there from 2.6.32-24 clear up to 3.2.0-31.
And I ran across some articles that suggested I could just use uname-r to identify my current
running kernel and that like I said that was 3.2.0-31.
There's some files in there for dash 32 but if you look they're not complete and I think
that's what work came off the rails it was trying to do a kernel I'll take ran out
of room but I found the article suggested I just delete files that don't match that number.
That really didn't seem prudent I did a little further research and fortunately I found
what seems to be a more elegant solution on upboot 2.com and links in the show notes
but it's www.utter up Ubuntu not up Ubuntu we just correct that my show note the dynamic
process as we go along doing the podcast www.upubuntu.com slash 2011 slash 11 slash how dash
2 dash remove dash unused dash old dash kernels dash on dot html apparently the html
the name of html file was based on the title of the well the title to gave the file inside
the document and it must be truncated okay first step from the articles verify you're
running kernel we already talked about that do you name dash are and like I said Linux
often keep older kernels so you can boot into an older version of grub and I mean this
is a fail safe you've probably seen that when you boot in your desktop there is a safe
version sometimes would be older kernel versions on your grub and that's self there's
a grub update and also nothing works you can't get in you can maybe try going back to
previous kernel and see if that'll let you in let you try to fix that it's fact for
iFF door has environment variable environment setting to let the OS or to tell the OS just
how many old kernels you want to maintain and that's a line install only underscore limit
and it's located in slash atc slash yum dot com and if anybody knows of now analog for
devian you boot to please please add it to the comments for this episode because I would
really like to know I look for couldn't find anything the reason for that is I would like
so I don't have to do this all time I would like to limit the server to two or three old
kernel versions and have it do its own cleanup I know about the I know about the install
only limit excuse me thanks for bearing with me still my cold still with me where was
I okay Linux will keep older kernels can be so you can both in emergency and both boot
into an older version of grub your from grub older kernel version from grub and I said
I found out if a door has environment setting to you can set just how many old kernels
you want to keep and oh mission to you on this I'm I'm wearing door 15 still I haven't had
time to to do the in place upgrade and my laptop here the one I'm actually working on right now
has brought home wireless and I tried to compile the driver for for the wireless card didn't have
much success and then all of a sudden boom got a kernel updated work this is right after I got
the machine so great you know the wireless work went on for a couple months like that boom
next kernel update and everyone since then wireless doesn't work so I've it's not not recommended
folks I tell you that I understand that but I've been booting into an older version the kernel
or the wireless work so I had to extend that variable to a ridiculous amount to avoid having
that kernel that I can actually use wiped out as the new ones come in uh okay so we've
views you name dot art to know what our current kernel is and then next step is list the
kernels currently installed on your system and you can do that with the package space dash dash
list space pipe space graph base Linux dash image so in other words you're looking for packages
that include Linux dash image those are your kernels or one of the files associated one of the
files associated with kernels and when I looked at that that put in that it was essentially all
those kernels that are in slash boot they were still installed and in use so the next step is
to call all the kernels but to kernel and please please this command that I'm about to give you
don't type it in by listing this podcast find the show notes on hacker public radio dot or
copy them for bames this worked for me uh doing that this way but it would be very very easy to
really mess up your system uh doing the wrong way or by making a mistake in the in this command
now but I'm not very good at reading regular expressions but I could see what was trying to do
there it what it's doing is again it's it's using the Linux image as a string to the core
and then right behind that of course is the kernel number what's doing is a comparison of the kernel
number to the same number it's returned by you name dash r and so it's returning all of those
limit links image files that do not match the current kernel version number and it's running that
through pseudu aptitude purge and so the command is pseudu space aptitude space dash capital p
space purge space tilde i Linux dash image dash backslash opening square bracket zero dash nine
backslash closing square back backslash opening parentheses backslash
bang character or explanation point whichever you want to call it backtick and that is the one
that's on the same key as the tilde the lower case generally a lot of keyboards you name space
dash r backtick backslash closing parentheses and in that whole thing from the end of herge and
there's a space and there's no other spaces in the whole rest of it except in the you name dash
r between the you name and the dash r of course so it's you know it's tilde i and then Linux
right there it's not there's no space there and my my particular contribution to this command
is the dash capital p after after aptitude because that will prompt you to confirm to take those
actions so if you if you look at what says it's going to purge and your current kernel version is
in there don't don't let it do it obviously finally the last step is make sure grub refresher changes
so the next man would be pseudu space update dash grub too and that just make sure that what's
in the grub configuration files hernal system there matches what you actually have now on your
system and really as it was going through the previous command as it was going through and eliminating
one kernel the time i i could see it updating grub at the end of each of those steps so i think
this is just to make really really sure everything everything is update so wouldn't eliminate this
last step but i think i think it's probably already all done for you this point now this is this
more than a week ago and it's worth noting i still don't have that s32 kernel update so it may have
told it well let's try to put in the third the dash 32 don't try it again that that may be a
consequence i'm i i'm going to take a wait and see attitude and if it never if it doesn't ever
seem to do a kernel update again i'm going to have to do something to kickstart it and get it
updating kernels and uh if i find out i need to do that and find out what i have to do make it do
that i'll add it to another podcast later but uh now last few last thing at the uh at the
in the show notes uh i did a df again and saved it and my slash boot is now 14%
the 100% and then below that i have the output of a directory listing on my slash boot and the
only kernel files that you see in there are associated with three dot two dot zero dash three one
okay like i said this is this worked for me work seem to work really well i am not usually a fan
of running command with a whole bunch of regular expressions without understanding exactly what
it was it was going to do the system but i thought with the dash p i was fairly safe turns turns
out it was so if you've got a devian or you boom to server because i don't think i'm running into this
on a desktop unless you've created a set slash boot so you may want to look in there it may be
maybe filling up with a bunch of kernels um worked for work for me uh your your mileage may
vary and buyer beware and all that so this been 5150 for hacker public radio have a great day
you can contact me at 5150 at linuxbasement.com you can uh find my other contact information
at the big red switch dot jubal garden dot com and stay happy to always see each other next time
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