101 apend. kernel
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This document provides an overview of Linux kernel concepts, including key components like the scheduler and memory manager. It discusses how the kernel is modular and allows functional blocks to be added or removed via modules. It also covers commands like lsmod, rmmod, insmod, and modprobe for working with kernel modules, as well as kernel boot and runtime parameters that can be configured using sysctl.
![CoreLinuxforRedHatandFedoralearningunderGNUFreeDocumentationLicense-Copyleft(c)AcácioOliveira2012
Everyoneispermittedtocopyanddistributeverbatimcopiesofthislicensedocument,changingisallowed
LSMOD
4
Kernel
lsmod Prints all of the currently loaded modules
[root@dev1 ~]# lsmod
Module Size Used by
ipv6 264608 20
binfmt_misc 14096 1
dm_multipath 21136 0
parport_pc 31724 0
lp 16576 0
parport 42252 2 parport_pc,lp
usbcore 129724 1
ext3 125968 1
jbd 61928 1 ext3
raid10 23808 0
raid456 119840 0
xor 10512 1 raid456
raid1 24064 0
raid0 10752 0
multipath 11776 0
linear 9088 0
dm_mirror 23016 0
dm_snapshot 18872 0
dm_mod 55752 3 dm_multipath,dm_mirror,dm_snapshot
processor 26412 0
fuse 42160 1
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101 apend. kernel
- 1. CoreLinuxforRedHatandFedoralearningunderGNUFreeDocumentationLicense-Copyleft(c)AcácioOliveira2012 Everyoneispermittedtocopyanddistributeverbatimcopiesofthislicensedocument,changingisallowed Linux Essenciais and System Administration
- 2. CoreLinuxforRedHatandFedoralearningunderGNUFreeDocumentationLicense-Copyleft(c)AcácioOliveira2012 Everyoneispermittedtocopyanddistributeverbatimcopiesofthislicensedocument,changingisallowed Key Knowledge Areas Process of kernel of the operating system kernel kernel Terms and Utilities kernel lsmod rmmod insmod modprobe depmod sysctl 2
- 3. CoreLinuxforRedHatandFedoralearningunderGNUFreeDocumentationLicense-Copyleft(c)AcácioOliveira2012 Everyoneispermittedtocopyanddistributeverbatimcopiesofthislicensedocument,changingisallowed Overview 3 The kernel represents the core of the operating system. Major components: •Scheduler •Memory manager •Device drivers •Filesystems •Networking Kernel Linux kernel is modular allowing functional blocks of software to be added or removed on fly via modules mechanism. Modules encompass functions such as: Device drivers Kernel features - firewalls, RAID, LVM Filesystems
- 4. CoreLinuxforRedHatandFedoralearningunderGNUFreeDocumentationLicense-Copyleft(c)AcácioOliveira2012 Everyoneispermittedtocopyanddistributeverbatimcopiesofthislicensedocument,changingisallowed LSMOD 4 Kernel lsmod Prints all of the currently loaded modules [root@dev1 ~]# lsmod Module Size Used by ipv6 264608 20 binfmt_misc 14096 1 dm_multipath 21136 0 parport_pc 31724 0 lp 16576 0 parport 42252 2 parport_pc,lp usbcore 129724 1 ext3 125968 1 jbd 61928 1 ext3 raid10 23808 0 raid456 119840 0 xor 10512 1 raid456 raid1 24064 0 raid0 10752 0 multipath 11776 0 linear 9088 0 dm_mirror 23016 0 dm_snapshot 18872 0 dm_mod 55752 3 dm_multipath,dm_mirror,dm_snapshot processor 26412 0 fuse 42160 1 Ex:
- 5. CoreLinuxforRedHatandFedoralearningunderGNUFreeDocumentationLicense-Copyleft(c)AcácioOliveira2012 Everyoneispermittedtocopyanddistributeverbatimcopiesofthislicensedocument,changingisallowed rmmod – insmod – modprobe - depmod 5 Kernel rmmod Removes (unloads) a loaded modules •Can not unload a module that is a dependency of another module. •Can not unload in-use modules. insmod Loads a module into the kernel. •Full pathname required. •Does not handle dependencies automatically. modprobe Intelligent module handler •Can load/unload modules. •Automatically handles dependencies. •Only need to specify name of module, not full path, when loading. depmod: Rebuilds module dependency lists
- 6. CoreLinuxforRedHatandFedoralearningunderGNUFreeDocumentationLicense-Copyleft(c)AcácioOliveira2012 Everyoneispermittedtocopyanddistributeverbatimcopiesofthislicensedocument,changingisallowed Kernel boot parameters 6 Kernel Hundreds of parameters can be passed to the kernel at boot time. Most common include: •root=/dev/sda3 Set the root device •quiet Reduce informational messages at startup •rhgb Red Hat Graphical Boot •console=ttyS0 Specify console device http://www.kernel.org/doc/Documentation/kernel-parameters.txt
- 7. CoreLinuxforRedHatandFedoralearningunderGNUFreeDocumentationLicense-Copyleft(c)AcácioOliveira2012 Everyoneispermittedtocopyanddistributeverbatimcopiesofthislicensedocument,changingisallowed Kernel runtime parameters 7 Kernel Numerous kernel parameters which can be adjusted at runtime, including: •net.ipv4.* •vm.* •kernel.* •fs.* SYSCTL sysctl Get/set kernel parameters sysctl –a produces a complete list of all tunable kernel parameters like networking, kernel, filesystem. •sysctl -w kernel.pid_max=65535 •sysctl -a •sysctl -w vm.swappiness=100