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Following is a quick-start guide for learning how to set up and use ELKS quickly, with a table of contents.
If something is missing you'd like to know about, please let us know.
The ELKS system must be booted up on PC-compatible hardware, or a PC emulator. There are a variety of binary images available, which are copied onto physical floppy disks or USB thumb drives for booting. The recommended image to use for first time users is a 1.44M floppy image intended for 3.5" disks, but can also be used with a PC emulator, such as qemu. This image is named fd1440.img. Following is the full list of binary images produced by the ELKS build (in the images/ directory), and will also be available for direct download:
Size Format Filename Description
----- ------ ---------------- -----------------------------------------------------
1440k Minix fd1440.img Build-configuration specific (uses ibmpc-1440.config)
360k Minix fd360-minix.img 5.25" floppy, 9 sectors, 2 heads
720k Minix fd720-minix.img 3.5" floppy, 9 sectors, 2 heads
1200k Minix fd1200-minix.img 3.5" floppy, 15 sectors, 2 heads
1440k Minix fd1440-minix.img 3.5" floppy, 18 sectors, 2 heads
2880k Minix fd2880-minix.img 3.5" floppy, 36 sectors, 2 heads
32MB Minix hd32-minix.img 32MB flat hard disk, CHS=63,16,63
32MB Minix hd32mbr-minix.img 32MB partitioned hd, CHS=63,16,63
360k FAT fd360-fat.img 5.25" floppy, 9 sectors, 2 heads
720k FAT fd720-fat.img 3.5" floppy, 9 sectors, 2 heads
1200k FAT fd1200-fat.img 3.5" floppy, 15 sectors, 2 heads
1440k FAT fd1440-fat.img 3.5" floppy, 18 sectors, 2 heads
2880k FAT fd2880-fat.img 3.5" floppy, 36 sectors, 2 heads
32MB FAT hd32-fat.img 32MB flat hard disk, CHS=63,16,63
32MB FAT hd32mbr-fat.img 32MB partitioned hd, CHS=63,16,63
1232k FAT fd1232-pc98.img 3.5" floppy, 1K sectors for PC-98
1440k FAT fd1440-pc98.img 3.5" floppy, 512 byte sectors for PC-98
Detailed information about the image content can be found in the configuration file: elkscmd/Applications
To copy a 1440k image onto a floppy from Linux, one could use dd if=fd1440.img of=/dev/fd0 bs=1024 count=1440. Please note that ELKS is built with certain parameters compiled in the kernel. An example is the network card's parameters. If you need to change these you will need to recompile the kernel.
ELKS can be installed on a hdd or floppy. The installation process supports the following filesystems: MINIX, FAT16 and FAT32. The basic stages are:
- Boot a binary image of ELKS
- Create a partition using fdisk command
- Format the partition
- Execute the sys command to transfer ELKS kernel and commands
- Reboot into your new installation
Example installation on /dev/hda1:
-
Start fdisk from a floppy binary image:
fdisk /dev/hdaUse thencommand to create a partition /dev/hda1 of size 200MB. Make it bootable withb. Save everything withw. Exit withq. -
Format the partition as FAT32 of size 180MB:
mkfat -fat32 /dev/hda1 180000To create a MINIX partition use mkfs instead. -
Copy the kernel and all basic files required to boot ELKS with the sys commande:
sys /dev/hda1. Use the -M option to put ELKS boot loader in the MBR. This is required if you are using an empty hard drive and you do not have another boot loader. -
reboot
Please note that using sys creates a minimalistic install. For example when installing from a 360kb image you will miss most of the commands from /bin, and some config files from /etc (such as net.cfg and mount.cfg). You may need to complement your installation by manually adding these files from another ELKS build image (e.g. hd32-fat.img).
For partitions less than 32MB FAT16 will be selected automatically by mkfat. Once you booted into your new installation you will need to copy yourself some additional commands to the hdd. If the ELKS boot manager does not know where is your new installation you can instruct it to boot from /dev/hda1 by pressing 1. You can also format a partition as FAT16 or FAT32 using Windows 10. Windows puts extra hidden files on the formatted drive such as the folder "System Volume Information". Normally ELKS sys tool is capable of installing ELKS on a drive with "System Volume Information", but in case of failed install, you can try formatting the partition under Linux to remove this folder. Dual boot of ELKS and DOS might also be possible. You can also try to write an HD image of ELKS directly to your hard drive.
Building ELKS from source code requires downloading and building a gcc cross-compiler for 8086, and then cloning the source repository from GitHub. Full instructions are here.
The ELKS system compilation is configured using make menuconfig, which allows a variety of technical options to be specified.
ELKS is booted by copying one of the floppy or hard disk images produced during the build directly to the media (usually using 'dd'), and can also be booted virtually using a PC emulator such as qemu. Both the native filesystem formats Minix (v1) as well as MSDOS FAT are supported, for both floppy disk, USB FAT and hard disks. The ELKS build process automatically adds the appropriate boot sector onto the created image.
When ELKS boots, the boot sector searches for /Linux on the root filesystem and loads it. It also searches for the file /bootopts, which contains boot options. A variety of boot options can be set in the /bootopts file, without requiring kernel recompilation.
ELKS boot options are parsed from a Linux 2.0-style multiple command lines stored in the root file /bootopts, and parsed at boot time to enable a variety of configurations without having to recompile anything. Very useful for debugging and quick configuration changes.
Allows setting the console to be serial (or any other device, such as virtual Alt2 /dev/tty2), root mount device (FAT and Minix), read-only/read-write, alternative startup process & args, init run level, network start, and set environment variables for the initial startup process, such as a shell or shell script. Note: if the kernel is compiled with serial console ON, console= redirection will have no effect.
Here's an example of the distribution /bootopts file, with everything commented out:
##
#console=ttyS0 root=fd0 net=ne2k 3 # condensed
#TZ=MDT7 # timezone
#QEMU=1 # to use ftp/ftpd in qemu
#init=/bin/init 3 # multiuser serial
#init=/bin/sh # singleuser shell
#LOCALIP=10.0.2.16
#HOSTNAME=elks16
#comirq=,,10,7 # IRQ-settings for COM1-4
#ne2k=9,0x300,0x80
#wd8003=3,0x280,0xD000,0x80
#3c509=9,0x330,0x80
#bufs=2500 # number of kernel buffers (XMS max 2500, EXT max 256)
#sync=30 # seconds per auto-sync
#console=ttyS0,19200 # serial console
#console=tty2 # alt2 console
#root=hda1 # hd partition 1
#ro # read-only root
#net=slip
For validation, the /bootopts file must start with ## and file size less be than 512 bytes. # = comment, options are space separated, multiple lines ok. Devices can be specified by /dev/ prefix or without. Non-reserved options without '=' inside them are treated as arguments to /bin/init or init=, and options with '=' are passed as environment variables to the init (or other init=) process.
Here's some more examples, hopefully self-explanatory:
init=/bin/init 3 or just 3
init=/bin/sh HOME=/ TERM=ansi
console=ttyS0, console=/dev/tty2, etc
console=ttyS0,38400
console=tty1
root=fd1, root=/dev/fd1, root=hda[1-4], hdb[1-4], hdc[1-4]
net=eth, net=slip, net=cslip starts predefined network configurations
ro, rw
comirq=,7 sets non-standard IRQ (7) on COM2
To use, edit the file elkscmd/rootfs_template/bootopts and run "make" to create another image, or edit /bootopts when running ELKS and reboot. More about runtime configuration options for network interface cards below.
The entire process can be configured in or out by selecting "Boot Options in /bootopts" in the Kernel section of make menuconfig, and is by default ON.
The provided shell script qemu.sh can be used to boot ELKS with any of the ELKS-produced disk images. This script is also used to redirect the serial port to the shell as well as provide additional images to mount after boot. See qemu.sh for more details, and uncomment the desired IMAGE= for the desired disk image. Running ./qemu.sh will run QEMU with the default options and boot the file 'images/fd1440.img'.
The ELKS boot process displays a '.' for each disk sector read, or a '*' for a disk sector retry. If an error occurs, a digit from 1 through 4 is displayed followed by '!'. The meaning of these error numbers is as follows:
1! - Disk read error, too many retries
2! - Can't read second sector of MINIX boot (no payload)
3! - No /linux system directory entry found (no system)
4! - Bad system file format (incorrect header or invalid /linux image)
ELKS supports single-user operation, as well as allowing multiple logins over the serial ports as well as virtual consoles. Virtual consoles all run on the main system display and can be switched between by using the ALT-Fnkey keyboard sequence, for instance ALT-F2 will switch to virtual console 2, which will have another login, if running in a multiuser run level.
Each mode of operation is called a run level and is assigned a number from 1 through 6, and the file /etc/inittab specifies which serial port or virtual console should be used for the login, along with some other parameters. The ELKS run levels are:
| Run Level | Description | Device(s) |
|---|---|---|
| 1 | Single User Console | tty1 only |
| 2 | Single User Serial | ttyS0 only |
| 3 | Multiuser Console and Serial | tty1,ttyS0 |
| 4 | Multiuser Serial | ttyS0,ttyS1 |
| 5 | Multiuser Console | tty1,tty2,tty3 |
| 6 | Multiuser All | tty1,tty2,tty3,ttyS0,ttyS1 |
The system can be switched to a new run level by specifying the new run level to init, e.g. init 3 will switch to multiuser serial.
The first line in the file /etc/inittab specifies the boot run level. By default, it is set to single user console (run level 1):
id:1:initdefault:
Additional lines in /etc/inittab specify which commands to run for a series of run levels. For instance, the following line specifies to run /bin/getty (the program that prints 'login:') on /dev/ttyS1 at 9600 baud, for run levels 4 and 6:
s1:46:respawn:/bin/getty /dev/ttyS1 9600
Two shells are available on ELKS. The standard shell sh is used when logging in as 'root', and provides a BASH-compatible scripting shell with modern capabilities including line editing using the arrow keys and TAB command completion. An alternative shell, sash (Stand Alone Shell), is provided for smaller-footprint use and is available when logging in as 'toor'. sash supports csh-like command-line history and editing, and has a number of builtin commands (such as ls, rm, mkdir, ...) for fast execution. The file /etc/passwd specifies which shell to run based on login name.
ELKS supports up to 4 serial ports, /dev/ttyS0 thru /dev/ttyS3 (COM1 - COM4) for use as logins, outbound terminal emulation to other systems, network connections (slip/cslip, see the Networking section below) and mouse connections for the Nano-X graphical window system.
Hardware flow Control is not supported. Serial speed up to 115200 is possible if the hardware can handle it. Speeds 38400 and 57600 have been found to work on vintage 286 and 386 based systems.
The default IRQ assignments for serial lines (set in the kernel configuration file elks/include/arch/ports.h) are 4,3,5,7. IRQs are assigned by ELKS when a device is opened, so having multiple devices configured to use the same IRQ is not a problem. Further, ELKS will detect available devices at boot time and ignore configuration data for non-existent devices.
The first two serial ports (COM1, COM2 or /dev/ttyS0 and /dev/ttyS1) may be configured (via make menuconfig, see the installation section above) to bypass parts of the low level driver in order to increase speed. This mode is meant for networking and file transfers and is not well suited for interactive use (logins).
ELKS includes a diagnostic/test program for serial ports named sercat, please refer to the manual page for details.
As discussed above in Logins, the serial ports can be turned on for logins by setting run level 3 by running init 3 at shell prompt.
The serial ports are exclusive use, so they cannot be used simultaneously for login or terminal emulation and a mouse. If a mouse is connected, running init 1 will turn off serial logins so the mouse can be used.
The first serial port, /dev/ttyS0, can be used for logins with QEMU by uncommenting one of the following lines in qemu.sh:
# Uncomment this to route ELKS /dev/ttyS0 to host terminal
CONSOLE="-serial stdio"
# Hides qemu window also
#CONSOLE="-serial stdio -nographic"
If the second line is also uncommented, QEMU won't display the graphical console.
Serial logins must be enabled by setting run level 3, either by editing the first line of /etc/inittab as follows, or running init 3 after boot:
id:3:initdefault:
To use the mouse with QEMU for ELKS, uncomment the following line in qemu.sh:
SERIAL="-chardev msmouse,id=chardev1 -device isa-serial,chardev=chardev1,id=serial1"
The host mouse will be setup as a serial mouse connected to /dev/ttyS0, which is the default for running the Nano-X graphical demos, such as nxlandmine, nxdemo or nxclock.
ELKS supports TCP/IP networking via a socket library in the kernel and a user mode networking stack ktcp. Several Ethernet card architectures are supported (check menuconfig for an updated list), plus serial connectivity via SLIP and CSLIP. Networking is started via the net script either at system start in /etc/rc.sys or via the command line. If 'net=eth' is present in /bootopts (MINIX FS only), networking will be started at boot time. Networking IP address and daemon configuration is specified in the /etc/net.cfg file or - optimally - in the /bootopts file.
Multiple network drivers can be compiled into the kernel. There are two, possibly three parameters to configure: IO base address, IRQ and - for some interfaces - RAM base address. Default values are used and they might differ from your network card configuration. Check the dip-switches or jumpers on your card (for soft-configured (PnP) cards, it may be necessary to run a DOS-based configuration utility in order to find and/or change the current settings). For all card types, IRQ and IO Base address (and RAM base address for shared memory cards) may be configured at runtime via the /bootopts file, see below.
The defaults are set in the header file elks/include/arch/ports.h, for example:
/* wd, wd.c*/
#define WD_IRQ 2
#define WD_PORT 0x240
#define WD_RAM 0xCE00 /* RAM base address */
If you make changes, recompile and use the new kernel. However, configuring the network interfaces via /bootopts is strongly recommended and much simpler. Use ne2k=irq,base, wd8003=irq,base,ram or 3c509=irq,base to set the correct values. The IRQ is a decimal number, the port address and shared memory address are hexadecimal and must be preceded by '0x'. Make sure the changes don't cause the size of the bootopts file to exceed 511 bytes. Also keep an eye on the boot messages while booting the system, to verify that the card is found and configured correctly.
For the ne2k and wd80xx cards, the configuration values you use must match those set in the card, either via soft-configuration (set via a software configuration tool) or via jumpers. The 3Com EL3/3C509 card uses the values you provide regardless of the setting on/in the card.
The ne2k driver will recognize an 8bit vs a 16bit card and act correspondingly. If you use a 16bit card in an 8bit bus, you need to tell the driver about it. Do that by setting the low bit of the card's IO-address in /bootopts. E.g. if the IOport address is 0x300, set it to 0x301.
All network cards will report overruns and/or lost packets under heavy load. This is unavoidable and rarely a problem except for performance.
Ethernet, SLIP and CSLIP link layers and the networking stack can be started quickly using the /bin/net shell script, which allows for specifying the link layer, and serial port and baud rate for SLIP/CSLIP. The default addresses of IP 10.0.2.15, gateway 10.0.2.2 and net mask 255.255.255.0 are used, but can be modified in the /etc/net.cfg script, as well as the default serial device and baud rate. Following is the usage for net as well as several examples:
net [start|stop|show] [ne2k|wd8003|3c509|slip|cslip] [baud] [device]
$ net start [starts ethernet networking on default NIC]
$ net show [show networking defaults]
$ net start wd8003 [starts ethernet networking on WD8003 NIC]
$ net start slip [starts slip networking on /dev/ttyS0 at 57600 baud]
$ net start slip 19200 /dev/ttyS1 [starts slip networking on /dev/ttyS1 at 19200 baud]
$ net start cslip 4800 [starts cslip networking on /dev/ttyS0 at 4800 baud]
The net start command also starts two daemons, telnetd and httpd, for TELNET port 23 and HTTP port 80 remote access.
The net script runs ktcp which is the actual user mode TCP/IP networking stack. For more direct control, ktcp can be run directly from the command line, as follows:
ktcp [-b] [-d] [-p ne2k|wd8003|3c509|slip|cslip] [-m mtu] [-s baud] [-l device] [localip] [gateway] [netmask]
-b run in background
-d debug mode
-p link layer NIC name, slip or cslip
-m specify MTU (default 1024)
-s baud rate
-l device for SLIP or CSLIP
# ktcp -b -p 3c509 10.0.2.15 10.0.2.2 255.255.255.0 [start ethernet networking on 3C509 NIC as IP 10.0.2.15]
# ktcp -b -p slip 10.0.2.15 10.0.2.2 255.255.255.0 [start slip networking]
# telnetd [start telnetd]
A shell script 'slattach.sh' is provided to help configure a remote Linux system for SLIP or CSLIP connectivity with ELKS.
After starting networking, the netstat and arp commands will display networking connections/statistics, and the ARP cache, respectively.
QEMU emulates the NE2K interface and needs specific options to forward incoming packets to the emulated system. Outgoing packets are forwarded by default.
The qemu.sh script sets up incoming IP packet forwarding for telnet on port 2323 and http on port 8080. This is configured using the following lines in qemu.sh, which also sets up the NE2K emulation network interface card to IRQ 12 (the default IO port address is 0x300):
# Simultaneous telnet and http forwarding
FWD="hostfwd=tcp:127.0.0.1:8080-10.0.2.15:80,hostfwd=tcp:127.0.0.1:2323-10.0.2.15:23"
NET="-netdev user,id=mynet,$FWD -device ne2k_isa,irq=12,netdev=mynet"
To access ELKS from Linux, use the following after starting networking using net start as described above:
$ telnet 10.0.2.15 2323 [telnet to ELKS from Linux]
or input "10.0.2.15:8080" in your browser [http to ELKS]
To access ELKS from macOS, use "localhost" rather than the QEMU default gateway 10.0.2.15:
$ telnet localhost 2323 [telnet to ELKS from macOS]
To telnet out from ELKS on QEMU to Linux or macOS, no host forwarding is needed as QEMU will auto-forward all outgoing packets, so use telnet as normal, and specify the IP address of your system and port, e.g.:
# telnet 192.168.179.176 23 [telnet from ELKS to host]
In some cases, your system may not have a telnetd server running. On macOS, homebrew can be used to download a telnetd server, which is easier to setup on (e.g.) port 2323 (actually any port > 1024 because the lower ports are protected by the system). Here it is being setup on port 23:
/usr/local/opt/telnetd/sbin/telnetd -debug 23 & (start homebrew telnetd on port 23 on macOS)
To telnet to ELKS telnetd from within ELKS, which now works great and supports multiple connections, connect to the ELKS IP (10.0.2.15) directly, localhost (127.0.0.1) or the machine name as given in /etc/localhost:
$ telnet 10.0.2.15 (telnet to ELKS from ELKS)
$ telnet localhost
$ telnet elks15
Check out the Networking: File transfers wiki for more information about ELKS and networking, file transfers in particular.
Details on ELKS internal process status can be seen by running the ps command:
# ps
elks17# ps
PID GRP TTY USER STAT CPU HEAP FREE SIZE COMMAND
1 0 root S 0 3072 2010 13072 /bin/init 3
13 13 1 root S 0 0 1980 8656 /bin/getty /dev/tty1
14 14 S0 root S 5 1188 13186 68960 -/bin/sh
15 15 S2 root S 0 0 1972 8656 /bin/getty /dev/ttyS2 57600
16 14 S0 root R 71 1024 1182 11824 ps
7 7 root S 0 1024 34748 76656 ktcp -b -p ne2k 10.0.2.17 10.0.2.2 255.255.255.0
9 9 root S 0 0 1994 9744 telnetd
11 11 root S 0 0 7320 28640 ftpd -d
This display shows process 1 /bin/init, which reads the /etc/inittab file and controls ELKS run levels. A getty process is running on /dev/tty1 (the console), which displays a 'login:' prompt and is awaiting a login. A login shell '-/bin/sh' is running on ttyS0.
The labels are PID and GRP for process ID and group, TTY shows the controlling terminal, USER is the user ID of the process, and the STAT column shows the process run status:
R running
S sleeping (waiting on read or child exit, etc)
s uninterruptible sleeping
T stopped
Z zombie (exited with saved exit status for parent)
E exiting
The HEAP and FREE columns show the process heap usage and (free) stack available, which are useful for tuning using the chmem command, explained below. The CPU column shows current CPU usage in %.
ELKS internal memory usage is displayed via meminfo:
# meminfo
HEAP TYPE SIZE SEG TYPE SIZE CNT
eb8a SEG 12 1eb2 BUF 65536 1
eb9e SEG 12 2eb2 CSEG 6816 1
ebb2 SEG 12 305c DSEG 8768 1
ebc6 SEG 12 3280 DSEG 12112 1
ebda free 12
ebee SEG 12 36c8 CSEG 6608 1
ec02 TTY 128
ec8a TTY 64
ecd2 SEG 12 3865 DSEG 6448 1
ece6 SEG 12 39f8 CSEG 4576 1
ecfa TTY 1024
f102 TTY 64
f14a SEG 12 3b16 free 7936 0
f15e SEG 12 3d06 CSEG 46224 1
f172 SEG 12 484f DSEG 18672 1
f186 SEG 12 4cde free 339488 0
f19a SEG 12 3575 free 5424 0
f1ae free 3666
Total heap 5246 Total mem 528608
Memory usage 517KB total, 172KB used, 345KB free
The HEAP column shows the kernel local heap address, memory segment type and size. Type SEG is a main memory segment, used for code (CSEG) and data (DSEG), and BUF (level 2 cache external file buffers). TTY segments are the variable-sized TTY (console, serial and PTY) input/output queues. The last lines show the total kernel local heap use, total memory installed, used and free.
ELKS is designed to use small, separate heap and stack areas for minimum RAM usage. The default heap and stack sizes are 2k bytes. The chmem command is useful for working with ps output to set and show the heap and stack usage for any process. To show the a programs settings, run chmem with no arguments:
# chmem /bin/vi
TEXT DATA BSS HEAP STACK TOTDATA TOTAL
62400 7008 26336 0 0 41536 103936 /bin/vi
The HEAP and STACK displayed as 0 indicate the system should use the default settings (2k each) for those values.
The following shows telnetd using a smaller heap and stack of 1k bytes:
# chmem /bin/telnetd
TEXT DATA BSS HEAP STACK TOTDATA TOTAL
5856 368 3568 1024 1024 5984 11840 /bin/telnetd
The native filesystem for ELKS is Minix v1, which support 14 character filenames. In addition, MSDOS FAT12, FAT16 and FAT32 filesystems are supported, with VFAT long filename support. The block device for mounting filesystems is /dev/hda for the first hard drive, and /dev/hdb for the second. Partitioned filesystems 1-4 are accessed by appending the digit to the block device, e.g. partition 2 on the first drive would be /dev/hda2. Floppy drives are /dev/fd0 for first floppy, and /dev/fd1 the second.
To mount a filesystem after booting ELKS, use the mount command and optionally specify the filesystem type, e.g.:
# mount /dev/fd1 /mnt [mount MINIX floppy B on /mnt]
# mount /dev/hda1 /mnt [mount MINIX hard drive partition 1 on /mnt]
# mount -t msdos /dev/fd1 /mnt [mount FAT floppy B on /mnt]
# mount -a /dev/fd1 /mnt [mount (MINIX or FAT) floppy B on /mnt]
As ov version 0.6.0 mount automatically detects the file system type, making the -a and -t options less important. Be sure to sync the data on drives before rebooting, and use umount /dev/fd1 to unmount the floppy after use. Entering mount without options lists the currently mounted file systems.
Here's a useful list of block device names, useful for mounting, or using the root= option in /bootopts:
/dev/hda first hard drive, no partitions
/dev/hda1 first hard drive, partition 1
/dev/hda2 first hard drive, partition 2
/dev/hda3 first hard drive, partition 3
/dev/hda4 first hard drive, partition 4
/dev/hdb second hard drive, no partitions
/deb/hdb1 second hard drive, partition 1
/dev/hdc usually USB drive
/dev/fd0 floppy A
/dev/fd1 floppy B
/dev/rd0 ramdisk A
/dev/rd1 ramdisk B
/dev/ssd SSD (ram or flash) disk
The following programs are useful for getting the most out of ELKS:
arp [display ARP cache]
ls /bin [list all commands]
grep [search a file for a string]
hd [hex dumper]
init 1 [turn off serial logins, or use mouse]
init 3 [turn on serial logins]
init 5 [turn on multiuser virtual console logins]
init 6 [turn on multiuser consoles and serial logins]
kilo [visual editor]
meminfo [show memory usage]
miniterm -s 19200 [login via serial to remote system at 19200 baud]
more [screen paginate through a file]
mount [attach a floppy or HD filesystem]
mouse [test mouse]
net start [start networking]
netstat [show networking statistics and connections]
printenv [show environment variables]
ps [display running processes]
reboot [reboot system in 3 seconds]
sync [write unwritten data to disk]
telnet [login via network to remote system]
vi [UNIX vi editor]
The following files and directories are used for ELKS configuration:
/etc/inittab [initial run level and login devices]
/etc/rc.sys [startup shell script, sets date and starts networking]
/etc/net.cfg [network configuration]
/etc/mount.cfg [auto-mounted or checked filesystems]
/etc/passwd [sets login users, user IDs and shells]
/etc/motd [build version message displayed at boot]
/etc/issue [ELKS version message displayed at login]
/etc/profile [global shell settings]
/root/.profile [root shell settings]
/bootopts [boot options]