Here's What To Do When The Above Happens To Your Linux Install!
**This article is a continuation of (iMac) Ubuntu Install Gone Wrong? Install by Hand! (1 of 2)**
Creating a Basic Linux Operating Environment
Linux requires a minimal set of files and directories to do its work. Thanks to the Ubuntu Trusty Tahir Install DVD, we have access to a semi-functioning operating system with almost everything we need. Here's an overview of the operating environment that the Ubuntu Trusty Tahir Install DVD creates:
There are many entries in this list. Some require special treatment, some don't:
Here are the directories we can simply create with the mkdir command:
/boot
/dev
/cdrom
/media/mnt
/proc
/sys
Here are the commands required to accomplish that:
Here's what the /mnt/hdd directory looked like after these operations:
Except for the /boot directory, these can all be left as they were created.
The following directories can be copied to the Linux partition via the command cp -a:
/bin
/etc
/home
/lib
/lib64
/opt
/root
/run
/sbin
/srv
/tmp
/usr
/var
Here's how that was done:
Here's what the /mnt/hdd directory looked like after all the operations:
OK, we are very close to being done. The work that remains is:
The broken links at the root of the Ubuntu Install file system are a clue of that; they are red because the target files are missing:
initrd.img -> initrd.img-4.4.0-31-generic
vmlinuz -> boot/vmlinuz-4.4.0-31-generic
These files are listed in an Ubuntu Packages page for Trusty Tahir.
The symbolic links indicate that the system once had initrd.img and vmlinuz files of version 4.4.0-31-generic installed in the /boot directory, but they have somehow gone missing. Here's what a "normal" /boot directory looks like. It's from silver, a post-install Linux Ubuntu Trusty Tahir (14.04.5) machine that I built some time ago. silver has since been upgraded a few times, and it shows. There are several different versions of initrd.img and vmlinuz files on it:
Looking over the silver file listing, it seems that sentinel needed the following files to be able to boot properly:
"In Linux, the System.map file is a symbol table used by the kernel. A symbol table is a look-up between symbol names and their addresses in memory. A symbol name may be the name of a variable or the name of a function"
-- https://en.wikipedia.org/wiki/System.map
abi:
"In computer software, an application binary interface (ABI) is the interface between two program modules, one of which is often a library or operating system, at the level of machine code. An ABI determines such details as how functions are called and in which binary format information should be passed from one program component to the next, or to the operating system in the case of a system call."
-- https://en.wikipedia.org/wiki/Application_binary_interface
config:
"The config file contains kernel configuration settings. It is created when a kernel is built with the “make menuconfig” command. The settings in this file are changed depending on the options selected in “make menuconfig” command. The contents of this file affect which modules are loaded when the kernel boots."
-- http://www.linuxnix.com/linux-directory-structure-explained-boot-folder
vmlinuz:
"vmlinuz is the name of the Linux kernel executable. A kernel is a program that constitutes the central core of a computer operating system. It is the first thing that is loaded into memory (which physically consists of RAM chips) when a computer is booted up (i.e., started), and it remains in memory for the entire time that the computer is in operation. An executable, also called an executable file, is a file that can be run as a program. vmlinuz is a compressed Linux kernel, and it is bootable."
-- http://www.linfo.org/vmlinuz.html
initrd.img:
"The initial RAM disk (initrd) is an initial root file system that is mounted prior to when the real root file system is available. The initrd is bound to the kernel and loaded as part of the kernel boot procedure. The kernel then mounts this initrd as part of the two-stage boot process to load the modules to make the real file systems available and get at the real root file system."
-- http://advancelinux.blogspot.hk/2013/06/what-is-initrd-image-in-linux.html
Eventually, I was able to find these files Ubuntu Trusty Tahir Install DVD, but the matter was made confusing by the fact that they had been saved without version numbers. They were located in the /cdrom/casper directory:
The next stage of the install is to change the root of the system to the hard disk. this is accomplished with the chroot command:
A little bit of tweaking is required to make the newly chroot-ed system functional:
Here's the commands to do it:
(https://superuser.com/questions/165116/mount-dev-proc-sys-in-a-chroot-environment)
A little bit of updating was necessary to make the newly chrooted system fully functional:
From this:
to this:
Don't forget to save your work. The following command will have the machine boot into text mode on boot:
(https://ubuntuforums.org/showthread.php?p=9644518#post9644518 )
The update-grub command is used to update the grub boot environment in preparation for installation on the preferred boot device (in our case, /dev/sda):
First, because we are operating in a chroot-ed environment, we need to re-install ssh on the machine:
Next, we need to make sure that ssh is available at all times. This is accomplished by programming the machine to start the ssh server at all runlevels (2-5) except for single-user mode (1), where having an ssh server available wouldn't make sense, because TCP/IP is usually turned off.
Here's the command to set the machine hostname:
Here's what my /etc/hosts file looked like once I had finished editing it.
From:
To:
root@sentinel:/# cat /etc/hosts
127.0.0.1 localhost
127.0.1.1 sentinel
# The following lines are desirable for IPv6 capable hosts
::1 ip6-localhost ip6-loopback
fe00::0 ip6-localnet
ff00::0 ip6-mcastprefix
ff02::1 ip6-allnodes
ff02::2 ip6-allrouters
ff02::3 ip6-allhosts
root@sentinel:/# ls -l
total 2
drwxr-xr-x 2 root root 2955 Aug 3 2016 bin
drwxr-xr-x 1 root root 60 Aug 3 2016 boot
dr-xr-xr-x 1 root root 2048 Aug 3 2016 cdrom
drwxr-xr-x 18 root root 4300 Mar 17 01:28 dev
drwxr-xr-x 1 root root 740 Mar 17 04:07 etc
drwxr-xr-x 1 root root 80 Mar 16 23:54 home
lrwxrwxrwx 1 root root 32 Aug 3 2016 initrd.img -> initrd.img-4.4.0-31-generic
drwxr-xr-x 1 root root 60 Aug 3 2016 lib
drwxr-xr-x 2 root root 43 Aug 3 2016 lib64
drwxr-xr-x 1 root root 60 Mar 16 23:49 media
drwxr-xr-x 1 root root 60 Mar 17 04:07 mnt
drwxr-xr-x 2 root root 3 Aug 3 2016 opt
dr-xr-xr-x 164 root root 0 Mar 16 23:48 proc
drwxr-xr-x 21 root root 338 Aug 3 2016 rofs
drwx------ 1 root root 80 Mar 17 00:10 root
drwxr-xr-x 22 root root 720 Mar 17 01:11 run
drwxr-xr-x 2 root root 4885 Aug 3 2016 sbin
drwxr-xr-x 2 root root 3 Aug 3 2016 srv
dr-xr-xr-x 13 root root 0 Mar 17 03:07 sys
drwxrwxrwt 4 root root 100 Mar 17 04:17 tmp
drwxr-xr-x 1 root root 120 Aug 3 2016 usr
drwxr-xr-x 1 root root 120 Aug 3 2016 var
lrwxrwxrwx 1 root root 29 Aug 3 2016 vmlinuz -> boot/vmlinuz-4.4.0-31-generic
There are many entries in this list. Some require special treatment, some don't:
- Certain directories (/dev, /proc and /sys) needn't be copied because they are virtual and/or created by the system when the kernel boots, they just need to be created so the kernel has something to "hook" onto.
- Certain directories (/cdrom, /mnt, /media) shouldn't be copied because they either contain the newly mounted hard disk (/mnt) or the Ubuntu Trusty Tahir Install DVD (/cdrom, /media) and just might potentially create a copy loop. They just need to be created.
- Certain directories (/rofs) are unique to the Ubuntu installation DVD and are not needed for a live Linux system.
- One directory (/boot) needs to be handled specially.
- The logical links (initrd.img & vmlinuz) are both broken and they will need to be (re)linked properly to files in the /boot directory, once those file are installed.
- The rest of the directories can simply be copied over with the cp command.
Directories to Create with mkdir:
Here are the directories we can simply create with the mkdir command:
/boot
/dev
/cdrom
/media/mnt
/proc
/sys
Here are the commands required to accomplish that:
root@sentinel:/# cd /mnt/hdd
root@sentinel:/mnt/hdd# mkdir bootroot@sentinel:/mnt/hdd# mkdir devroot@sentinel:/mnt/hdd# mkdir cdrom
root@sentinel:/mnt/hdd# mkdir media
root@sentinel:/mnt/hdd# mkdir mnt
root@sentinel:/mnt/hdd# mkdir proc
root@sentinel:/mnt/hdd# mkdir sys
root@sentinel:/mnt/hdd# mkdir bootroot@sentinel:/mnt/hdd# mkdir devroot@sentinel:/mnt/hdd# mkdir cdrom
root@sentinel:/mnt/hdd# mkdir media
root@sentinel:/mnt/hdd# mkdir mnt
root@sentinel:/mnt/hdd# mkdir proc
root@sentinel:/mnt/hdd# mkdir sys
Here's what the /mnt/hdd directory looked like after these operations:
root@sentinel:/mnt/hdd# ls -l
total
40
drwxr-xr-x
2 root root 4096 Mar 17 04:34 boot
drwxr-xr-x
18 root root 4380 Mar 22 01:53 dev
drwxr-xr-x
2 root root 4096 Mar 17 04:34 cdrom
drwx------
2 root root 16384 Mar 17 01:31 lost+found
drwxr-xr-x
2 root root 4096 Mar 17 09:27 media
drwxr-xr-x
2 root root 4096 Mar 17 04:34 mnt
drwxr-xr-x
2 root root 4096 Mar 17 04:34 proc
drwxr-xr-x
2 root root 4096 Mar 17 04:34 sys
Except for the /boot directory, these can all be left as they were created.
Directories to Copy with cp:
The following directories can be copied to the Linux partition via the command cp -a:
/bin
/etc
/home
/lib
/lib64
/opt
/root
/run
/sbin
/srv
/tmp
/usr
/var
Here's how that was done:
root@sentinel:/mnt/hdd# cp -a /bin .
root@sentinel:/mnt/hdd# cp -a /etc .
root@sentinel:/mnt/hdd# cp -a /home .
root@sentinel:/mnt/hdd# cp -a /lib .
root@sentinel:/mnt/hdd# cp -a /lib64 .
root@sentinel:/mnt/hdd# cp -a /opt .
root@sentinel:/mnt/hdd# cp -a /root .
root@sentinel:/mnt/hdd# cp -a /run .
root@sentinel:/mnt/hdd# cp -a /sbin .
root@sentinel:/mnt/hdd# cp -a /srv .
root@sentinel:/mnt/hdd# cp -a /tmp .
root@sentinel:/mnt/hdd# cp -a /usr .
root@sentinel:/mnt/hdd# cp -a /var .
root@sentinel:/mnt/hdd# cp -a /etc .
root@sentinel:/mnt/hdd# cp -a /home .
root@sentinel:/mnt/hdd# cp -a /lib .
root@sentinel:/mnt/hdd# cp -a /lib64 .
root@sentinel:/mnt/hdd# cp -a /opt .
root@sentinel:/mnt/hdd# cp -a /root .
root@sentinel:/mnt/hdd# cp -a /run .
root@sentinel:/mnt/hdd# cp -a /sbin .
root@sentinel:/mnt/hdd# cp -a /srv .
root@sentinel:/mnt/hdd# cp -a /tmp .
root@sentinel:/mnt/hdd# cp -a /usr .
root@sentinel:/mnt/hdd# cp -a /var .
Here's what the /mnt/hdd directory looked like after all the operations:
root@sentinel:/mnt/hdd# ls -l
total 96
drwxr-xr-x 2 root root 4096 Aug 3 2016 bin
drwxr-xr-x 3 root root 4096 Mar 19 07:26 boot
drwxr-xr-x 2 root root 4096 Mar 17 04:34 cdrom
drwxr-xr-x 18 root root 4380 Mar 22 01:53 dev
drwxr-xr-x 132 root root 12288 Mar 22 01:53 etc
drwxr-xr-x 4 root root 4096 Mar 16 23:54 home
drwxr-xr-x 27 root root 4096 Mar 21 14:42 lib
drwxr-xr-x 2 root root 4096 Mar 21 14:42 lib64
drwx------ 2 root root 16384 Mar 17 01:31 lost+found
drwxr-xr-x 4 root root 4096 Mar 21 14:41 media
drwxr-xr-x 2 root root 4096 Mar 17 04:34 mnt
drwxr-xr-x 2 root root 4096 Aug 3 2016 opt
dr-xr-xr-x 149 root root 0 Mar 22 01:52 proc
drwx------ 19 root root 4096 Mar 21 14:48 root
drwxr-xr-x 21 root root 720 Mar 22 01:56 run
drwxr-xr-x 2 root root 12288 Mar 21 09:39 sbin
drwxr-xr-x 2 root root 4096 Aug 3 2016 srv
dr-xr-xr-x 13 root root 0 Mar 22 02:36 sys
drwxrwxrwt 4 root root 80 Mar 22 02:17 tmp
drwxr-xr-x 11 root root 4096 Mar 21 14:42 usr
drwxr-xr-x 13 root root 4096 Aug 3 2016 var
total 96
drwxr-xr-x 2 root root 4096 Aug 3 2016 bin
drwxr-xr-x 3 root root 4096 Mar 19 07:26 boot
drwxr-xr-x 2 root root 4096 Mar 17 04:34 cdrom
drwxr-xr-x 18 root root 4380 Mar 22 01:53 dev
drwxr-xr-x 132 root root 12288 Mar 22 01:53 etc
drwxr-xr-x 4 root root 4096 Mar 16 23:54 home
drwxr-xr-x 27 root root 4096 Mar 21 14:42 lib
drwxr-xr-x 2 root root 4096 Mar 21 14:42 lib64
drwx------ 2 root root 16384 Mar 17 01:31 lost+found
drwxr-xr-x 4 root root 4096 Mar 21 14:41 media
drwxr-xr-x 2 root root 4096 Mar 17 04:34 mnt
drwxr-xr-x 2 root root 4096 Aug 3 2016 opt
dr-xr-xr-x 149 root root 0 Mar 22 01:52 proc
drwx------ 19 root root 4096 Mar 21 14:48 root
drwxr-xr-x 21 root root 720 Mar 22 01:56 run
drwxr-xr-x 2 root root 12288 Mar 21 09:39 sbin
drwxr-xr-x 2 root root 4096 Aug 3 2016 srv
dr-xr-xr-x 13 root root 0 Mar 22 02:36 sys
drwxrwxrwt 4 root root 80 Mar 22 02:17 tmp
drwxr-xr-x 11 root root 4096 Mar 21 14:42 usr
drwxr-xr-x 13 root root 4096 Aug 3 2016 var
OK, we are very close to being done. The work that remains is:
- Deal With the /boot Directory
- Create the vmlinuz and initrd.img Symbolic Links
- Copy update-initramfs from rofs directory
- Chroot the system to /mnt/hdd
- Configure and (re)Install grub
- Ensure ssh is available on boot
- Set hostname and /etc/hosts
- Eject Install DVD
- Confirm Everything & Cold (re)Start
Deal With the /boot Directory
The /boot directory is really important, because it's where all of the Linux startup files are kept. Unfortunately, the /boot directory that is set up by the Ubuntu Install DVD is missing critical files (vmlinuz, initrd.img).The broken links at the root of the Ubuntu Install file system are a clue of that; they are red because the target files are missing:
initrd.img -> initrd.img-4.4.0-31-generic
vmlinuz -> boot/vmlinuz-4.4.0-31-generic
These files are listed in an Ubuntu Packages page for Trusty Tahir.
The symbolic links indicate that the system once had initrd.img and vmlinuz files of version 4.4.0-31-generic installed in the /boot directory, but they have somehow gone missing. Here's what a "normal" /boot directory looks like. It's from silver, a post-install Linux Ubuntu Trusty Tahir (14.04.5) machine that I built some time ago. silver has since been upgraded a few times, and it shows. There are several different versions of initrd.img and vmlinuz files on it:
root@silver:/boot# ls -l
total 98900
-rw-r--r-- 1 root root 1208829 Jun 29 2016 abi-3.16.0-77-generic
-rw-r--r-- 1 root root 1245512 Feb 20 22:14 abi-4.4.0-64-generic
-rw-r--r-- 1 root root 1245512 Mar 4 04:19 abi-4.4.0-66-generic
-rw-r--r-- 1 root root 171880 Jun 29 2016 config-3.16.0-77-generic
-rw-r--r-- 1 root root 190255 Feb 20 22:14 config-4.4.0-64-generic
-rw-r--r-- 1 root root 190255 Mar 4 04:19 config-4.4.0-66-generic
drwxr-xr-x 5 root root 4096 Mar 19 21:11 grub
-rw-r--r-- 1 root root 20202512 Feb 11 17:10 initrd.img-3.16.0-77-generic
-rw-r--r-- 1 root root 22284925 Mar 2 11:33 initrd.img-4.4.0-64-generic
-rw-r--r-- 1 root root 22284241 Mar 12 12:07 initrd.img-4.4.0-66-generic
-rw-r--r-- 1 root root 176500 Mar 12 2014 memtest86+.bin
-rw-r--r-- 1 root root 178176 Mar 12 2014 memtest86+.elf
-rw-r--r-- 1 root root 178680 Mar 12 2014 memtest86+_multiboot.bin
-rw------- 1 root root 3520509 Jun 29 2016 System.map-3.16.0-77-generic
-rw------- 1 root root 3897401 Feb 20 22:14 System.map-4.4.0-64-generic
-rw------- 1 root root 3897401 Mar 4 04:19 System.map-4.4.0-66-generic
-rw------- 1 root root 6376256 Jun 29 2016 vmlinuz-3.16.0-77-generic
-rw------- 1 root root 6989456 Feb 20 22:14 vmlinuz-4.4.0-64-generic
-rw------- 1 root root 6989392 Mar 4 04:19 vmlinuz-4.4.0-66-generic
total 98900
-rw-r--r-- 1 root root 1208829 Jun 29 2016 abi-3.16.0-77-generic
-rw-r--r-- 1 root root 1245512 Feb 20 22:14 abi-4.4.0-64-generic
-rw-r--r-- 1 root root 1245512 Mar 4 04:19 abi-4.4.0-66-generic
-rw-r--r-- 1 root root 171880 Jun 29 2016 config-3.16.0-77-generic
-rw-r--r-- 1 root root 190255 Feb 20 22:14 config-4.4.0-64-generic
-rw-r--r-- 1 root root 190255 Mar 4 04:19 config-4.4.0-66-generic
drwxr-xr-x 5 root root 4096 Mar 19 21:11 grub
-rw-r--r-- 1 root root 20202512 Feb 11 17:10 initrd.img-3.16.0-77-generic
-rw-r--r-- 1 root root 22284925 Mar 2 11:33 initrd.img-4.4.0-64-generic
-rw-r--r-- 1 root root 22284241 Mar 12 12:07 initrd.img-4.4.0-66-generic
-rw-r--r-- 1 root root 176500 Mar 12 2014 memtest86+.bin
-rw-r--r-- 1 root root 178176 Mar 12 2014 memtest86+.elf
-rw-r--r-- 1 root root 178680 Mar 12 2014 memtest86+_multiboot.bin
-rw------- 1 root root 3520509 Jun 29 2016 System.map-3.16.0-77-generic
-rw------- 1 root root 3897401 Feb 20 22:14 System.map-4.4.0-64-generic
-rw------- 1 root root 3897401 Mar 4 04:19 System.map-4.4.0-66-generic
-rw------- 1 root root 6376256 Jun 29 2016 vmlinuz-3.16.0-77-generic
-rw------- 1 root root 6989456 Feb 20 22:14 vmlinuz-4.4.0-64-generic
-rw------- 1 root root 6989392 Mar 4 04:19 vmlinuz-4.4.0-66-generic
Looking over the silver file listing, it seems that sentinel needed the following files to be able to boot properly:
- System.map
- abi
- config
- vmlinuz
- initrd.img
What do These Files Do?
System.map:"In Linux, the System.map file is a symbol table used by the kernel. A symbol table is a look-up between symbol names and their addresses in memory. A symbol name may be the name of a variable or the name of a function"
-- https://en.wikipedia.org/wiki/System.map
abi:
"In computer software, an application binary interface (ABI) is the interface between two program modules, one of which is often a library or operating system, at the level of machine code. An ABI determines such details as how functions are called and in which binary format information should be passed from one program component to the next, or to the operating system in the case of a system call."
-- https://en.wikipedia.org/wiki/Application_binary_interface
config:
"The config file contains kernel configuration settings. It is created when a kernel is built with the “make menuconfig” command. The settings in this file are changed depending on the options selected in “make menuconfig” command. The contents of this file affect which modules are loaded when the kernel boots."
-- http://www.linuxnix.com/linux-directory-structure-explained-boot-folder
vmlinuz:
"vmlinuz is the name of the Linux kernel executable. A kernel is a program that constitutes the central core of a computer operating system. It is the first thing that is loaded into memory (which physically consists of RAM chips) when a computer is booted up (i.e., started), and it remains in memory for the entire time that the computer is in operation. An executable, also called an executable file, is a file that can be run as a program. vmlinuz is a compressed Linux kernel, and it is bootable."
-- http://www.linfo.org/vmlinuz.html
initrd.img:
"The initial RAM disk (initrd) is an initial root file system that is mounted prior to when the real root file system is available. The initrd is bound to the kernel and loaded as part of the kernel boot procedure. The kernel then mounts this initrd as part of the two-stage boot process to load the modules to make the real file systems available and get at the real root file system."
-- http://advancelinux.blogspot.hk/2013/06/what-is-initrd-image-in-linux.html
What Files Do We Have?
We have the following files:
root@sentinel:/#
cd /boot
root@sentinel:/boot#
ls -1 /boot/*-generic
/boot/abi-4.4.0-31-generic
/boot/config-4.4.0-31-generic
/boot/System.map-4.4.0-31-generic
/boot/abi-4.4.0-31-generic
/boot/config-4.4.0-31-generic
/boot/System.map-4.4.0-31-generic
What Files Are Missing?
We are missing the following files:
vmlinuz-4.4.0-31-generic
initrd.img-4.4.0-31-generic
initrd.img-4.4.0-31-generic
Eventually, I was able to find these files Ubuntu Trusty Tahir Install DVD, but the matter was made confusing by the fact that they had been saved without version numbers. They were located in the /cdrom/casper directory:
root@sentinel:/# cd /cdrom/casper root@sentinel:/cdrom/casper# ls -l total 1061139 -r--r--r-- 1 root root 61004 Aug 3 2016 filesystem.manifest -r--r--r-- 1 root root 1067 Aug 3 2016 filesystem.manifest-remove -r--r--r-- 1 root root 11 Aug 3 2016 filesystem.size -r--r--r-- 1 root root 1055989760 Aug 3 2016 filesystem.squashfs -r--r--r-- 1 root root 933 Aug 3 2016 filesystem.squashfs.gpg -r--r--r-- 1 root root 23614105 Aug 3 2016 initrd.lz -r--r--r-- 1 root root 6937248 Aug 3 2016 vmlinuz
Finding vmlinuz-4.4.0-31-generic:
How could I be so sure that the vmlinuz file I found in the /cdrom/casper was the right one? Because I checked it against existing vmlinuz versions by file size (6937248). After doing some research, I found out that there was only one vmlinuz file of that exact size, and that was vmlinuz-4.4.0-31-generic. Its even listed on this Ubuntu documentation page, which contains the following:
18 -rw-r--r-- 1 root root 6937248 Des 20 22:49 vmlinuz-
Another important consideration was that the listed vmlinuz matched the version of the kernel that was currently running on senintel:
So I felt pretty safe in my feeling that the vmlinuz file in /cdrom/casper was version actually vmlinuz-4.4.0-31-generic. So I copied the file it to the /boot directory with the proper version annotation:
Huh?
The file I was looking for was initrd.img, not initrd.lz - was there going to be a problem? As it turns out, no, but it took quite some time for me to discover what exactly an initrd.img file was and what formats it could come in (.gz, .lz). In the end, I determined that I could copy the file over to the /boot directory with a different extension and the proper version annotation:
Now I had all of the files I thought I needed to boot Linux:
root@sentinel:/boot# uname -a
Linux sentinel 4.4.0-31-generic #50~14.04.1-Ubuntu SMP Wed Jul 13 01:07:32 UTC 2016 x86_64 x86_64 x86_64 GNU/LinuxSo I felt pretty safe in my feeling that the vmlinuz file in /cdrom/casper was version actually vmlinuz-4.4.0-31-generic. So I copied the file it to the /boot directory with the proper version annotation:
root@sentinel:/# cd /mnt/hdd/boot
root@sentinel:/mnt/hdd/boot# cp /cdrom/casper/vmlinuz ./vmlinuz-4.4.0-31-generic
root@sentinel:/mnt/hdd/boot# cp /cdrom/casper/vmlinuz ./vmlinuz-4.4.0-31-generic
Finding initrd.img-4.4.0-31-generic:
With vmlinuz installed, I only needed initrd.img-4.4.0-31-generic to complete my complement of needed boot files. As I had already found a version of initrd in the /cdrom/casper directory, I looked at it:
root@sentinel:/mnt/hdd/boot# ls -l /cdrom/casper/initrd.lz
-r--r--r-- 1 root root 23614105 Aug 3 2016 /cdrom/casper/initrd.lz
-r--r--r-- 1 root root 23614105 Aug 3 2016 /cdrom/casper/initrd.lz
Huh?
The file I was looking for was initrd.img, not initrd.lz - was there going to be a problem? As it turns out, no, but it took quite some time for me to discover what exactly an initrd.img file was and what formats it could come in (.gz, .lz). In the end, I determined that I could copy the file over to the /boot directory with a different extension and the proper version annotation:
root@sentinel:/mnt/hdd/boot# cp /cdrom/casper/initrd.lz ./initrd.img-4.4.0-31-generic
Now I had all of the files I thought I needed to boot Linux:
root@sentinel:/mnt/hdd/boot# ls -1
abi-4.4.0-31-generic
config-4.4.0-31-generic
initrd.img-4.4.0-31-generic
System.map-4.4.0-31-generic
vmlinuz-4.4.0-31-generic
abi-4.4.0-31-generic
config-4.4.0-31-generic
initrd.img-4.4.0-31-generic
System.map-4.4.0-31-generic
vmlinuz-4.4.0-31-generic
Create the vmlinuz and initrd.img Symbolic Links
One of the easier tasks in this list is to create the symbolic links at the root of the filesystem to their counterparts in the /boot subdirectory:
root@sentinel:/# cd /mnt/hdd
root@sentinel:/mnt/hdd# ln -s ./boot/vmlinuz-4.4.0-31-generic vmlinuz
root@sentinel:/mnt/hdd# ln -s ./boot/initrd.img-4.4.0-31-generic initrd.img
root@sentinel:/mnt/hdd# ln -s ./boot/initrd.img-4.4.0-31-generic initrd.img
Copy update-initramfs from rofs directory
Another tweak that's needed to make things fully functional to copy update-initramfs from /rofs/usr/sbin to /mnt/hdd/usr/sbin. Why? Because the one copied from the live filesystem at /usr/sbin/update-initramfs is a "stub" that is not functional. It does not call mkinitramfs, instead it just issues a little error message:
root@sentinel:~# cd /usr/sbin
root@sentinel:/usr/sbin# ls update-initramfs
update-initramfs
root@sentinel:/usr/sbin# ls -l update-initramfs
-rwxr-xr-x 1 root root 87 Mar 16 23:49 update-initramfs
root@sentinel:/usr/sbin# cat update-initramfs
#! /bin/sh
echo "update-initramfs is disabled since running on read-only media"
exit 0
root@sentinel:/usr/sbin# cp /rofs/usr/sbin/update-initramfs /mnt/hdd/usr/sbin
root@sentinel:/usr/sbin# ls update-initramfs
update-initramfs
root@sentinel:/usr/sbin# ls -l update-initramfs
-rwxr-xr-x 1 root root 87 Mar 16 23:49 update-initramfs
root@sentinel:/usr/sbin# cat update-initramfs
#! /bin/sh
echo "update-initramfs is disabled since running on read-only media"
exit 0
root@sentinel:/usr/sbin# cp /rofs/usr/sbin/update-initramfs /mnt/hdd/usr/sbin
chroot the System (to /mnt/hdd)
root@sentinel:/# mkdir /mnt/hdd
root@sentinel:/# mount /dev/sda2 /mnt/hdd
root@sentinel:/# chroot /mnt/hdd
Tweak the Newly chroot-ed System:
A little bit of tweaking is required to make the newly chroot-ed system functional:
- Re-establish /proc:
- Re-establish /sys:
- Re-establish /dev:
- Re-establish /dev/pts:
Here's the commands to do it:
root@sentinel:/# mount -t proc proc /proc
root@sentinel:/# mount -t sysfs sys /sys
root@sentinel:/# mount -o bind /dev /dev
root@sentinel:/# mount -t devpts devpts /dev/pts
Housekeeping
A little bit of updating was necessary to make the newly chrooted system fully functional:
root@sentinel:/# apt-get update
.
.
.
(lots of output)
root@sentinel:/# apt-get install aptitude
.
.
.
(lots of output)
Configure & (re)Install grub
Now we need to provision and install the Ubuntu grub (actually grub2) system so that the system comes up normally. grub is the system that actually manages how the computer boots Linux. Most of the configuration files for grub are located at /boot/grub, but a very important grub configuration file is also located at /etc/default/grub. It needs some changes made.From this:
# If you change this file, run 'update-grub' afterwards to update
# /boot/grub/grub.cfg.
# For full documentation of the options in this file, see:
# info -f grub -n 'Simple configuration'
GRUB_DEFAULT=0
GRUB_HIDDEN_TIMEOUT=0
GRUB_HIDDEN_TIMEOUT_QUIET=true
GRUB_TIMEOUT=10
GRUB_DISTRIBUTOR=`lsb_release -i -s 2> /dev/null || echo Debian`
GRUB_CMDLINE_LINUX_DEFAULT="quiet splash"
GRUB_CMDLINE_LINUX=""
# Uncomment to enable BadRAM filtering, modify to suit your needs
# This works with Linux (no patch required) and with any kernel that obtains
# the memory map information from GRUB (GNU Mach, kernel of FreeBSD ...)
#GRUB_BADRAM="0x01234567,0xfefefefe,0x89abcdef,0xefefefef"
# Uncomment to disable graphical terminal (grub-pc only)
#GRUB_TERMINAL=console
# The resolution used on graphical terminal
# note that you can use only modes which your graphic card supports via VBE
# you can see them in real GRUB with the command `vbeinfo'
#GRUB_GFXMODE=640x480
# Uncomment if you don't want GRUB to pass "root=UUID=xxx" parameter to Linux
#GRUB_DISABLE_LINUX_UUID=true
# Uncomment to disable generation of recovery mode menu entries
#GRUB_DISABLE_RECOVERY="true"
# Uncomment to get a beep at grub start
#GRUB_INIT_TUNE="480 440 1"
to this:
# If you change this file, run 'update-grub' afterwards to update
# /boot/grub/grub.cfg.
# For full documentation of the options in this file, see:
# info -f grub -n 'Simple configuration'
GRUB_DEFAULT=0
#GRUB_HIDDEN_TIMEOUT=0
#GRUB_HIDDEN_TIMEOUT_QUIET=true
GRUB_TIMEOUT=0
GRUB_DISTRIBUTOR=`lsb_release -i -s 2> /dev/null || echo Debian`
GRUB_CMDLINE_LINUX_DEFAULT="quiet splash text"
GRUB_CMDLINE_LINUX="text"
# Uncomment to enable BadRAM filtering, modify to suit your needs
# This works with Linux (no patch required) and with any kernel that obtains
# the memory map information from GRUB (GNU Mach, kernel of FreeBSD ...)
#GRUB_BADRAM="0x01234567,0xfefefefe,0x89abcdef,0xefefefef"
# Uncomment to disable graphical terminal (grub-pc only)
GRUB_TERMINAL=console
# The resolution used on graphical terminal
# note that you can use only modes which your graphic card supports via VBE
# you can see them in real GRUB with the command `vbeinfo'
#GRUB_GFXMODE=640x480
# Uncomment if you don't want GRUB to pass "root=UUID=xxx" parameter to Linux
#GRUB_DISABLE_LINUX_UUID=true
# Uncomment to disable generation of recovery mode menu entries
#GRUB_DISABLE_RECOVERY="true"
# Uncomment to get a beep at grub start
#GRUB_INIT_TUNE="480 440 1"
Don't forget to save your work. The following command will have the machine boot into text mode on boot:
GRUB_CMDLINE_LINUX_DEFAULT="quiet splash text"
(https://ubuntuforums.org/showthread.php?p=9644518#post9644518 )
Prepare the New Boot Environment With update-grub:
The update-grub command is used to update the grub boot environment in preparation for installation on the preferred boot device (in our case, /dev/sda):
root@sentinel:/boot/grub# update-grub
Generating grub configuration file ...
Found linux image: /boot/vmlinuz-4.4.0-31-generic
Found initrd image: /boot/initrd.img-4.4.0-31-generic
done
Install the New Boot Environment With grub-install:
The grub-install command is used to install grub on the preferred boot device (in our case, /dev/sda):root@sentinel:/boot/grub# grub-install /dev/sda
Installing for i386-pc platform.
Installation finished. No error reported.
Ensure SSH is Available on (re)Boot:
The one thing that we want to be absolutely sure of is that the Secure Shell (ssh) service is available after a reboot, because this iMac has a history of video driver problems and a console that is unusable about 90% of the time.First, because we are operating in a chroot-ed environment, we need to re-install ssh on the machine:
root@sentinel:/etc/default# apt-get install --reinstall ssh
Reading package lists... Done
Building dependency tree
Reading state information... Done
0 upgraded, 0 newly installed, 1 reinstalled, 0 to remove and 223 not upgraded.
Need to get 0 B/1,118 B of archives.
After this operation, 0 B of additional disk space will be used.
(Reading database ... 178224 files and directories currently installed.)
Preparing to unpack .../ssh_1%3a6.6p1-2ubuntu2.8_all.deb ...
Unpacking ssh (1:6.6p1-2ubuntu2.8) over (1:6.6p1-2ubuntu2.8) ...
Setting up ssh (1:6.6p1-2ubuntu2.8) ...
Reading package lists... Done
Building dependency tree
Reading state information... Done
0 upgraded, 0 newly installed, 1 reinstalled, 0 to remove and 223 not upgraded.
Need to get 0 B/1,118 B of archives.
After this operation, 0 B of additional disk space will be used.
(Reading database ... 178224 files and directories currently installed.)
Preparing to unpack .../ssh_1%3a6.6p1-2ubuntu2.8_all.deb ...
Unpacking ssh (1:6.6p1-2ubuntu2.8) over (1:6.6p1-2ubuntu2.8) ...
Setting up ssh (1:6.6p1-2ubuntu2.8) ...
Next, we need to make sure that ssh is available at all times. This is accomplished by programming the machine to start the ssh server at all runlevels (2-5) except for single-user mode (1), where having an ssh server available wouldn't make sense, because TCP/IP is usually turned off.
root@sentinel:/# cd /mnt/hdd/etc/rc2.d
root@sentinel:/mnt/hdd/etc/rc2.d# ln -s ../init.d/ssh S99ssh
root@sentinel:/mnt/hdd/etc/rc2.d# cd ../rc3.d
root@sentinel:/mnt/hdd/etc/rc3.d# ln -s ../init.d/ssh S99ssh
root@sentinel:/mnt/hdd/etc/rc3.d# cd ../rc4.d
root@sentinel:/mnt/hdd/etc/rc4.d# ln -s ../init.d/ssh S99ssh
root@sentinel:/mnt/hdd/etc/rc4.d# cd ../rc5.d
root@sentinel:/mnt/hdd/etc/rc5.d# ln -s ../init.d/ssh S99ssh
root@sentinel:/mnt/hdd/etc/rc5.d# cd ../rc5.d
root@sentinel:/mnt/hdd/etc/rc2.d# ln -s ../init.d/ssh S99ssh
root@sentinel:/mnt/hdd/etc/rc2.d# cd ../rc3.d
root@sentinel:/mnt/hdd/etc/rc3.d# ln -s ../init.d/ssh S99ssh
root@sentinel:/mnt/hdd/etc/rc3.d# cd ../rc4.d
root@sentinel:/mnt/hdd/etc/rc4.d# ln -s ../init.d/ssh S99ssh
root@sentinel:/mnt/hdd/etc/rc4.d# cd ../rc5.d
root@sentinel:/mnt/hdd/etc/rc5.d# ln -s ../init.d/ssh S99ssh
root@sentinel:/mnt/hdd/etc/rc5.d# cd ../rc5.d
Set hostname and /etc/hosts
To prevent confusion at a later date, the name of the computer needs to be changed to whatever name you have decided on. For me, the choice was sentinel. To make the name change permanent, I needed to do a couple of things:- I needed to change the hostname
- I needed to edit /etc/hosts to make sure sentinel was correctly listed
Here's the command to set the machine hostname:
root@sentinel:/# hostname sentinel
Here's what my /etc/hosts file looked like once I had finished editing it.
From:
root@sentinel:/# cat /etc/hosts
127.0.0.1 localhost
127.0.1.1 ubuntu
# The following lines are desirable for IPv6 capable hosts
::1 ip6-localhost ip6-loopback
fe00::0 ip6-localnet
ff00::0 ip6-mcastprefix
ff02::1 ip6-allnodes
ff02::2 ip6-allrouters
ff02::3 ip6-allhosts
127.0.0.1 localhost
127.0.1.1 ubuntu
# The following lines are desirable for IPv6 capable hosts
::1 ip6-localhost ip6-loopback
fe00::0 ip6-localnet
ff00::0 ip6-mcastprefix
ff02::1 ip6-allnodes
ff02::2 ip6-allrouters
ff02::3 ip6-allhosts
To:
root@sentinel:/# cat /etc/hosts
127.0.0.1 localhost
127.0.1.1 sentinel
# The following lines are desirable for IPv6 capable hosts
::1 ip6-localhost ip6-loopback
fe00::0 ip6-localnet
ff00::0 ip6-mcastprefix
ff02::1 ip6-allnodes
ff02::2 ip6-allrouters
ff02::3 ip6-allhosts
Eject Install DVD
At this point, the Install DVD is no longer needed and can be removed with the eject command:
root@sentinel:/boot/grub# eject
Confirm Everything & Cold (re)Start
OK, take a deep breath. Now it's time to make sure that all of the things mentioned in this document were checked off, one by one. Once that's done, it's time to test the newly configured system with a cold start.This can be accomplished with the shutdown command:
root@sentinel:/boot/grub# shutdown -P now
root@sentinel:/boot/grub#
Broadcast message from graham@sentinel
(/dev/pts/0) at 13:29 ...
root@sentinel:/boot/grub#
Broadcast message from graham@sentinel
(/dev/pts/0) at 13:29 ...
After it powers down, the iMac can be turned back on by pressing the power button that is located on the rear lower left corner. You should hear a signature "iMac chime" and you will need to wait for about a minute for the machine to fully boot, during which you may see a parade of crazy looking screens:
- A persistent operating environment that retains the changes that were made
- A consistently presented command prompt without any lockups, freezing and weird looking screens
- ssh access so the operator has a vector to resolve matters in case something strange does happen
Success
Here's what sentinel looked like after this tutorial was done:
finis
References
Ubuntu 14.04, 13.10: Boot into Text Mode / Console / Command Line
http://ubuntuhandbook.org/index.php/2014/01/boot-into-text-console-ubuntu-linux-14-04/
low resolution in plymouth screen with nvidia-current
https://bugs.launchpad.net/ubuntu/+source/nvidia-graphics-drivers/+bug/565980
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