How large a /boot recommended for 21.10?

[raif]

How large a /boot partition is now recommended for Ubunutu?

I set my boot partition at 500M as that seemed ample when I bought my laptop a couple of years ago and various internet searches said 300M was fine. But now when I try to upgrade I get the message:


The upgrade needs a total of 376 M free space on disk '/boot'.

I have removed all but the current kernel, set compression to xz but even then I'm nearly 50Mb short. So it seems like I'll need to resize to be able to upgrade rather than do a fresh install. What size boot is now sensible to have, as I don't want to need to resize again in a year or two?

NB it's a dual boot machine with W10 and encrypted using:

https://help.ubuntu.com/community/ManualFullSystemEncryption

thanks!

[yancek]

If it's a dual boot with windows 10, it should be an EFI system, is that correct?

Do you also have a separate /boot partition in addition to the EFI partition? If so, why?

Post the output of the 2 following commands here as they will list useful information so you can get some help.


sudo parted -l
df -h

[raif]

many thanks - NB I followed the advice in the link above on manual encryption.


odel: ATA HFS512G39MND-351 (scsi)
Disk /dev/sda: 512GB
Sector size (logical/physical): 512B/4096B
Partition Table: gpt
Disk Flags:

Number Start End Size File system Name Flags
1 1049kB 274MB 273MB fat32 EFI System Partition boot, esp
2 274MB 290MB 16.8MB Microsoft reserved partition msftres
3 290MB 64.9GB 64.6GB ntfs Basic data partition msftdata
4 64.9GB 91.1GB 26.2GB system
5 91.1GB 512GB 421GB data


Model: SMI USB DISK (scsi)
Disk /dev/sdb: 8053MB
Sector size (logical/physical): 512B/512B
Partition Table: gpt
Disk Flags:

Number Start End Size File system Name Flags
1 32.8kB 3112MB 3112MB ISO9660 hidden, msftdata
2 3112MB 3116MB 4334kB Appended2 boot, esp
3 3116MB 3116MB 307kB Gap1 hidden, msftdata
4 3118MB 8053MB 4935MB ext4


Model: Linux device-mapper (linear) (dm)
Disk /dev/mapper/data-home: 421GB
Sector size (logical/physical): 512B/4096B
Partition Table: loop
Disk Flags:

Number Start End Size File system Flags
1 0.00B 421GB 421GB ext4


Error: /dev/mapper/data: unrecognised disk label
Model: Linux device-mapper (crypt) (dm)
Disk /dev/mapper/data: 421GB
Sector size (logical/physical): 512B/4096B
Partition Table: unknown
Disk Flags:

Model: Linux device-mapper (linear) (dm)
Disk /dev/mapper/system-boot: 537MB
Sector size (logical/physical): 512B/4096B
Partition Table: loop
Disk Flags:

Number Start End Size File system Flags
1 0.00B 537MB 537MB ext4


Model: Linux device-mapper (linear) (dm)
Disk /dev/mapper/system-root: 25.7GB
Sector size (logical/physical): 512B/4096B
Partition Table: loop
Disk Flags:

Number Start End Size File system Flags
1 0.00B 25.7GB 25.7GB ext4


Error: /dev/mapper/system: unrecognised disk label
Model: Linux device-mapper (crypt) (dm)
Disk /dev/mapper/system: 26.2GB
Sector size (logical/physical): 512B/4096B
Partition Table: unknown
Disk Flags:



and then


tmpfs 1.2G 2.2M 1.2G 1% /run
/dev/mapper/system-root 24G 18G 5.1G 78% /
tmpfs 5.8G 187M 5.6G 4% /dev/shm
tmpfs 5.0M 4.0K 5.0M 1% /run/lock
tmpfs 4.0M 0 4.0M 0% /sys/fs/cgroup
/dev/mapper/system-boot 488M 134M 319M 30% /boot
/dev/sda1 256M 40M 217M 16% /boot/efi
/dev/mapper/data-home 385G 235G 131G 65% /home
tmpfs 1.2G 5.4M 1.2G 1% /run/user/1000
cryfs@/home/####/Private 133G 1.4G 131G 1% /home/#####/.SiriKali/Private

[TheFu]

There are different needs for different system setups.

/boot/efi is recommended to be 500MB by some respected people. I've never used more than 20MB, so it seems like 10x too much. The more you dual boot and the more different OSes, the larger the efi needs to be.

Most people wouldn't have a separate /boot/ partition. I use LVM and sometimes I use encrypted LVM. Historically, that required a separate, unencrypted, /boot/ partition. If that partition is shared between different Linuxen, then it may need to be larger than smaller. Here's what I've setup on a few different systems:
Systems migrated from 12.04 --> 14.04 ---> 16.04 --> 18.04


Filesystem Type Size Used Avail Use% Mounted on
/dev/vda1 ext2 720M 140M 544M 21% /boot

/dev/sdb1 ext2 720M 165M 519M 25% /boot

/dev/sde2 ext2 237M 124M 101M 56% /boot

20.04 system - no separate /boot needed:

/dev/mapper/vgubuntu--mate-root ext4 19G 11G 7.6G 58% /
/dev/vda1 vfat 511M 7.1M 504M 2% /boot/efi

I've been planning to load up a 21.10 play VM today. I'll do that now. Give me a 30 minutes.

[ActionParsnip]

What is the output of:


uname -a
dpkg -l | grep linux-image

Thanks

[TheFu]

Fresh 21.10 full Ubuntu Gnome4 DE install, where I selected LVM onto a 29G storage area:


$ df -Th
Filesystem Type Size Used Avail Use% Mounted on
/dev/mapper/vgubuntu-root ext4 27G 6.5G 20G 26% /
/dev/vda2 vfat 512M 5.3M 507M 2% /boot/efi

No separate boot needed or used by default.

$ sudo lvs
LV VG Attr LSize Pool Origin Data% Meta% Move Log Cpy%Sync Convert
root vgubuntu -wi-ao---- <27.54g
swap_1 vgubuntu -wi-ao---- 980.00m


$ du -shc /boot
du: cannot read directory '/boot/efi': Permission denied
71M /boot
71M total

If you clean up old kernels and only patch weekly, then 500MB should fine to hold 4 kernels (that 1 per week, for 1 month of kernels). Just run sudo apt autoremove at least monthly. Every other week, if you want to be more cautious. If you patch daily and get 7 new kernels a week, you'll either want a larger /boot/ or need to run the autoremove every 4 days or so.

[GhX6GZMB]

Interesting discussion.
I just checked my /boot, it's 207 MiB in size. CORRECTION: that's the directory. I don't have a /boot partition.
I've never done anything with it, so this is the size defined by the Lubuntu 20.04 installer (single-boot machine).

[raif]

Thanks, yes this is a useful discussion. I still don't understand why I'm getting the message that I need 376Mb in boot to install 21.10 though, that seems a lot based on the posts above.

Using LVM shouldn't make a difference to space requirements surely? Though of course it might mean you need to partition differently and, as a result, might come up against partition size issues more often.

In terms of why I have a separate /boot, it's what I understood was needed for full manual encryption. If there's an simpler way to install Ubuntu on an encrypted hard drive, I'll do it when I get my next laptop. But hoping the performance benefits of 21.10 mean that date is further away ;)

uname -r gives



5.11.0-37-generic #41-Ubuntu SMP Mon Sep 20 16:39:20 UTC 2021 x86_64 x86_64 x86_64 GNU/Linux

and dpkg



ii linux-image-5.11.0-37-generic 5.11.0-37.41 amd64 Signed kernel image generic
rc linux-image-5.8.0-50-generic 5.8.0-50.56 amd64 Signed kernel image generic
ii linux-image-generic 5.11.0.37.39 amd64 Generic Linux kernel image
rc linux-image-unsigned-5.11.0-34-generic 5.11.0-34.36 amd64 Linux kernel image for version 5.11.0 on 64 bit x86 SMP
rc linux-image-unsigned-5.11.0-37-generic 5.11.0-37.41 amd64 Linux kernel image for version 5.11.0 on 64 bit x86 SMP

[TheFu]

What files are actually in /boot/? Have any old kernels been abandoned there? Not removed?
Removed and purged aren't the same to the package manager. It could be that the system has 4 kernels using space. Purged kernels don't show up in the APT/dpkg lists. Removed kernels may not remove headers and modules and extra-module packages as well.
For example:

$ dpkg -l linux-image*
Desired=Unknown/Install/Remove/Purge/Hold
| Status=Not/Inst/Conf-files/Unpacked/halF-conf/Half-inst/trig-aWait/Trig-pend
|/ Err?=(none)/Reinst-required (Status,Err: uppercase=bad)
||/ Name Version Architecture Description
+++-=====================================-============-============-=================================
un linux-image <none> <none> (no description available)
ii linux-image-5.4.0-86-generic 5.4.0-86.97 amd64 Signed kernel image generic
ii linux-image-5.4.0-88-generic 5.4.0-88.99 amd64 Signed kernel image generic
ii linux-image-generic 5.4.0.88.92 amd64 Generic Linux kernel image
un linux-image-unsigned-5.4.0-86-generic <none> <none> (no description available)
un linux-image-unsigned-5.4.0-88-generic <none> <none> (no description available)
Shows that there are only 2 kernels installed on this 20.04 (non-HWE) system. If I check /boot/, there are just 2 kernels:

-rw------- 1 root root 11776256 Sep 17 14:51 vmlinuz-5.4.0-86-generic
-rw------- 1 root root 11776256 Sep 23 12:41 vmlinuz-5.4.0-88-generic
There are some symbolic links to current and old, but those hit those 2 files above. Same for the initrd.img for each kernel.

By keeping 2 separate kernel lines, the package manager will plan to upgrade both of those lines with each upgrade command. Haven't both 5.8.x and 5.11.x kernel lines, effectively doubles the amount of storage in /boot/ required for an new kernel upgrade if both lines have updates. By purging the 5.8.x line and all modules, headers, and other dependencies, you'll half the /boot storage needed. Did you do an do-release-upgrade or a fresh install? I think I know the answer.

I know nothing about manual encryption. It appears to me that there is an unsupported encryption mode being used, not LUKs, which is supported.
LVM lets us have 50 LVs, inside 1 partition, so that would actually help with the constraints and difficulties in altering partitions. Also, the entire PV is often placed inside a single encrypted container when LUKs is used, so we get the benefits of having the entire OS and data inside that PV, VG and all LVs encrypted.

I've never seen the point of manually encrypting the OS. The only reason I can see that as a need would be in a dual boot setup, which I solve by using virtualization, so the VMs are all encrypted under the storage managed by the hostOS running the hypervisor.

Manually encrypting external storage does have a place too, but that is relatively simple with LUKs to setup to allow automatic decryption when connected to our systems, but manual decryption when connected to foreign computers. Https://baldnerd.com/add-a-drive-to-linux-and-encrypt-it has a guide for this.

[hk42]

The most I have seen is three kernels plus two low latency kernels if you use ubuntu studio.
If you want to compile your own kernels you must have room to test them.
IMHO it doesn't deserve a separate partition.