之前在这个贴子（Linux内核升级失败后回退）提到我升级内核遇到了问题，导致系统无法启动。后边又尝试了几次依旧同样的报错。最近又有了新的内核版本，现在跨版本升级，还是失败。研究好久才搞明白根本原因。原来是升级过几次后服务器/boot分区满了，所以当再次升级适合就遇到奇怪的报错。
Filesystem Size Used Avail Use% Mounted on udev 445M 0 445M 0% /dev tmpfs 98M 1.1M 97M 2% /run /dev/sda3 20G 5.8G 13G 32% / tmpfs 490M 0 490M 0% /dev/shm tmpfs 5.0M 0 5.0M 0% /run/lock tmpfs 490M 0 490M 0% /sys/fs/cgroup /dev/sda2 371M 309M 35M 91% /boot /dev/loop1 56M 56M 0 100% /snap/core18/2751 /dev/loop2 56M 56M 0 100% /snap/core18/2785 /dev/loop3 64M 64M 0 100% /snap/core20/1891 /dev/loop0 45M 45M 0 100% /snap/certbot/3024 /dev/loop4 74M 74M 0 100% /snap/core22/750 /dev/loop6 45M 45M 0 100% /snap/certbot/2913 /dev/loop5 74M 74M 0 100% /snap/core22/766 /dev/loop7 54M 54M 0 100% /snap/snapd/19457 /dev/loop8 174M 174M 0 100% /snap/lxd/25086 /dev/loop9 171M 171M 0 100% /snap/lxd/24918 /dev/loop10 54M 54M 0 100% /snap/snapd/19361 /dev/loop11 64M 64M 0 100% /snap/core20/1950 tmpfs 98M 0 98M 0% /run/user/1000
可以看到这个服务器虽然提供20G的内存，但是/boot分区只有371M，并且用掉了91%。当再安装新的内核时候，就会由于内存满了而失败。
我们可以将除当前使用内核之外的旧内核删除掉，再进行新的内核升级。先查下现在所用的内核版本：uname -a
Linux audicdn 5.4.0-144-generic #161-Ubuntu SMP Fri Feb 3 14:49:04 UTC 2023 x86_64 x86_64 x86_64 GNU/Linux
查询系统中共安装了哪些内核：apt list *linux* –installed
Listing... Done console-setup-linux/focal,now 1.194ubuntu3 all [installed,automatic] libselinux1/focal,now 3.0-1build2 amd64 [installed,automatic] linux-base/focal-updates,now 4.5ubuntu3.7 all [installed,automatic] linux-firmware/now 1.187.36 all [installed,upgradable to: 1.187.39] linux-headers-5.4.0-139-generic/focal-updates,focal-security,now 5.4.0-139.156 amd64 [installed,automatic] linux-headers-5.4.0-139/focal-updates,focal-security,now 5.4.0-139.156 all [installed,automatic] linux-image-5.4.0-139-generic/focal-updates,focal-security,now 5.4.0-139.156 amd64 [installed,automatic] linux-image-5.4.0-144-generic/focal-updates,focal-security,now 5.4.0-144.161 amd64 [installed,automatic] linux-modules-5.4.0-139-generic/focal-updates,focal-security,now 5.4.0-139.156 amd64 [installed,automatic] linux-modules-5.4.0-144-generic/focal-updates,focal-security,now 5.4.0-144.161 amd64 [installed,automatic] linux-modules-extra-5.4.0-139-generic/focal-updates,focal-security,now 5.4.0-139.156 amd64 [installed,automatic]
可看到除了144内核外，系统中还有139旧内核。现在我们将其卸载掉：
sudo apt purge linux-headers-5.4.0-139-generic linux-headers-5.4.0-139 linux-image-5.4.0-139-generic linux-modules-5.4.0-139-generic linux-modules-extra-5.4.0-139-generic
然后更新一下grub：
sudo update-grub
查看一下内存：
Filesystem Size Used Avail Use% Mounted on udev 445M 0 445M 0% /dev tmpfs 98M 1.1M 97M 2% /run /dev/sda3 20G 5.4G 13G 30% / tmpfs 490M 0 490M 0% /dev/shm tmpfs 5.0M 0 5.0M 0% /run/lock tmpfs 490M 0 490M 0% /sys/fs/cgroup /dev/sda2 371M 209M 135M 61% /boot /dev/loop1 56M 56M 0 100% /snap/core18/2751 /dev/loop2 56M 56M 0 100% /snap/core18/2785 /dev/loop3 64M 64M 0 100% /snap/core20/1891 /dev/loop0 45M 45M 0 100% /snap/certbot/3024 /dev/loop4 74M 74M 0 100% /snap/core22/750 /dev/loop6 45M 45M 0 100% /snap/certbot/2913 /dev/loop5 74M 74M 0 100% /snap/core22/766 /dev/loop7 54M 54M 0 100% /snap/snapd/19457 /dev/loop8 174M 174M 0 100% /snap/lxd/25086 /dev/loop9 171M 171M 0 100% /snap/lxd/24918 /dev/loop10 54M 54M 0 100% /snap/snapd/19361 /dev/loop11 64M 64M 0 100% /snap/core20/1950 tmpfs 98M 0 98M 0% /run/user/1000
可看到boot空间腾出来了。
接下来升级就好了：
sudo apt update sudo apt upgrage
现在不报错了，顺利完成升级。