Last night I switched HDs on my Gentoo laptop. In the process of doing this, I reset the bios… this was a bad idea, as I had used efibootmgr to setup my UEFI firmware to boot Linux.<\/p>\n\n\n\n
Now, at this point the reasonable thing to do is boot from a usb stick, chroot into the Gentoo install and either re-run efibootmgr or install grub… I didn’t have a usb stick\/other installation media handy… I did however have a SSD with Debian installed. My laptop only has 1 SATA bay however (both the Gentoo install and the Debian install are on SATA drives). These notes document what I did, in case I need to do this again in the future…<\/p>\n\n\n\n
So… I decided to boot into Debian. Create a ramdisk with a working Debian install, chroot to this. Then swap in the Gentoo SSD, chroot to the Gentoo install and install grub. This post documents my notes on this process.<\/p>\n\n\n\n
First boot into Debian, then as root create a ramdisk.<\/p>\n\n\n\n
swapoff\nmount -t tmpfs -o size=2048m none \/mnt\/ramdisk<\/pre>\n\n\n\nI probably could have used debbootstrap or something else… but I decided to copy everything I needed across manually. First I setup the dev,sys and proc directories:<\/p>\n\n\n\n
cd \/mnt\/ramdisk\nmkdir dev\nmkdir sys\nmkdir proc\nmount --rbind \/dev .\/dev\nmount --rbind \/sys .\/sys\nmount --rbind \/proc .\/proc<\/pre>\n\n\n\nNow copy across files needed for a more or less working system:<\/p>\n\n\n\n
cp -r \/etc .\ncp -r \/bin .\ncp -r \/sbin .\nmkdir usr\ncp -r \/usr\/bin .\/usr\ncp -r \/usr\/sbin .\/usr\ncp -r \/lib64 .\ncp -r \/lib .<\/pre>\n\n\n\nIn order to setup grub, I also needed the vfat module and 437 codepage modules. It’s easier to load them now…<\/p>\n\n\n\n
modprobe vfat\nmodprobe nls_cp437<\/pre>\n\n\n\nNext we pivot_root to use our new ramdisk… I guess chrooting will work too…<\/p>\n\n\n\n
mkdir \/tmp\/ramdisk\/old_root\npivot_root \/tmp\/ramdisk \/tmp\/ramdisk\/old_root<\/pre>\n\n\n\nYou can also chroot into the ramdisk… but if you exit and re-login you should be in the new root (you might need to restart login…).<\/p>\n\n\n\n
I now pulled out the Debian SATA drive (there’s probably a way to umount it cleanly… I didn’t… this is bad don’t do it). And inserted the Gentoo drive.<\/p>\n\n\n\n
Mount the gentoo drive somewhere and chroot into it:<\/p>\n\n\n\n
mkdir gentoo;mount \/dev\/sdb5 .\/gentoo\ncd gentoo\nmount --rbind \/dev .\/dev\nmount --rbind \/sys .\/sys\nmount --rbind \/proc .\/proc\nchroot gentoo<\/pre>\n\n\n\nWithin the gentoo install you should be able to install grub, or do whatever else you want to do. For me the grub install commands are:<\/p>\n\n\n\n
mount \/boot\ngrub-install \/dev\/sda --target=x86_64-efi --efi-directory=\/boot --removable\ngrub-mkconfig -o \/boot\/grub\/grub.cfg<\/pre>\n\n\n\nMy laptop (Lenovo x230) doesn’t boot unless I used –removable.<\/p>\n","protected":false},"excerpt":{"rendered":"
Last night I switched HDs on my Gentoo laptop. In the process of doing this, I reset the bios… this was a bad idea, as I had used efibootmgr to setup my UEFI firmware to boot Linux. Now, at this point the reasonable thing to do is boot from a usb stick, chroot into the […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"jetpack_post_was_ever_published":false,"_jetpack_newsletter_access":"","_jetpack_dont_email_post_to_subs":false,"_jetpack_newsletter_tier_id":0,"_jetpack_memberships_contains_paywalled_content":false,"_jetpack_memberships_contains_paid_content":false,"footnotes":"","jetpack_publicize_message":"","jetpack_publicize_feature_enabled":true,"jetpack_social_post_already_shared":true,"jetpack_social_options":{"image_generator_settings":{"template":"highway","default_image_id":0,"font":"","enabled":false},"version":2}},"categories":[1],"tags":[],"class_list":["post-5647","post","type-post","status-publish","format-standard","hentry","category-uncategorized"],"jetpack_publicize_connections":[],"jetpack_featured_media_url":"","jetpack_shortlink":"https:\/\/wp.me\/p1RRoU-1t5","jetpack_sharing_enabled":true,"_links":{"self":[{"href":"https:\/\/41j.com\/blog\/wp-json\/wp\/v2\/posts\/5647","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/41j.com\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/41j.com\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/41j.com\/blog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/41j.com\/blog\/wp-json\/wp\/v2\/comments?post=5647"}],"version-history":[{"count":1,"href":"https:\/\/41j.com\/blog\/wp-json\/wp\/v2\/posts\/5647\/revisions"}],"predecessor-version":[{"id":5648,"href":"https:\/\/41j.com\/blog\/wp-json\/wp\/v2\/posts\/5647\/revisions\/5648"}],"wp:attachment":[{"href":"https:\/\/41j.com\/blog\/wp-json\/wp\/v2\/media?parent=5647"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/41j.com\/blog\/wp-json\/wp\/v2\/categories?post=5647"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/41j.com\/blog\/wp-json\/wp\/v2\/tags?post=5647"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}