dandan's questions

the command

yum updateinfo list

running well on redhat 6 and 7 as the following

  yum updateinfo list
  Loaded plugins: product-id, rhnplugin, subscription-manager
  This system is receiving updates from RHN Classic or Red Hat Satellite.
  RHEA-2015:2461 enhancement Red_Hat_Enterprise_Linux-Release_Notes-7-en-US-      7-2.el7.noarch
  RHBA-2015:2371 bugfix      alsa-tools-firmware-1.0.28-2.el7.x86_64
  RHBA-2015:2403 bugfix      authconfig-6.2.8-10.el7.x86_64
  RHBA-2015:2144 bugfix      bash-4.2.46-19.el7.x86_64

but on redhat 5.X

I get the following results because updateinfo not defined on redhat 5

  #  yum updateinfo list
  Loaded plugins: rhnplugin, security
  This system is receiving updates from RHN Classic or RHN Satellite.
  usage: yum [options] COMMAND

  List of Commands:

  check-update   Check for available package updates
  clean          Remove cached data
  deplist        List a package's dependencies
  downgrade      downgrade a package
  erase          Remove a package or packages from your system
  groupinfo      Display details about a package group
  groupinstall   Install the packages in a group on your system

as all know with uptime we can capture the days that machine is up

# uptime
12:08:19 up 93 days, 14:12,  1 user,  load average: 0.38, 0.36, 0.40

what we actually need is to know the date of the reboot / restart

for example - 21/5/2016 12:98

uptime command not have the right flags to do that , so maybe with other commands ?

but after google searching I not find what I want ,

So I will happy to get any suggestion

I have linux redhat machine

# more /etc/redhat-release
Red Hat Enterprise Linux Server release 5.11 (Tikanga)

I want to change the hwclock to UTC time

So I perform little test as

# date -u
Tue Jul 26 10:01:53 UTC 2016

more /etc/sysconfig/clock
ZONE="Asia/Tokyo"

hwclock --show
Tue Jul 26 19:02:17 2016  -0.768566 seconds

And now I will set the hwclock to UTC

hwclock --systohc --utc

But the hwclock not change to UTC time ?

# hwclock --show
Tue Jul 26 19:02:56 2016  -0.534987 seconds

I also change the /etc/sysconfig/clock and append the line UTC=yes

 # vi /etc/sysconfig/clock

 # more /etc/sysconfig/clock
 ZONE="Asia/Tokyo"
 UTC=yes

But from hwclock -- show I get non UTC time

 # hwclock --show
 Tue Jul 26 19:06:56 2016  -0.786752 seconds

I try again by the following command but without success

 # hwclock --systohc --utc

 # hwclock --show
 Tue Jul 26 19:07:07 2016  -0.399765 seconds

I reboot the machine to see if I get UTC hwclock after restart but without success

 # reboot

 Broadcast message from root (pts/0) (Tue Jul 26 19:07:13 2016):

 The system is going down for reboot NOW!

After machine reboot I perform the following , but still cant configure hwclock to UTC -:(

 # hwclock --show
 Tue Jul 26 19:11:05 2016  -0.697674 seconds

 # hwclock --systohc --utc

 # hwclock --show
 Tue Jul 26 19:11:15 2016  -0.838524 seconds

Please advise why I not get UTC time by the hwclock command

Machine HW info

# dmidecode | grep -i hp
       Vendor: HP
       Manufacturer: HP
       Manufacturer: HP
HP ProLiant System/Rack Locator
HP BIOS PXE NIC PCI and MAC Information
HP BIOS iSCSI NIC PCI and MAC Information

I run the hwclock with debug as:

  hwclock --systohc --utc --debug
  hwclock from util-linux-2.13-pre7
  Using /dev/rtc interface to clock.
  Last drift adjustment done at 1469527871 seconds after 1969
  Last calibration done at 1469527871 seconds after 1969
  Hardware clock is on UTC time
  Assuming hardware clock is kept in UTC time.
  Waiting for clock tick...
  /dev/rtc does not have interrupt functions. Waiting in loop for time   from /dev/rtc to change
 ...got clock tick
  Time read from Hardware Clock: 2016/07/26 11:17:36
  Hw clock time : 2016/07/26 11:17:36 = 1469531856 seconds since 1969
  Time elapsed since reference time has been 0.993984 seconds.
  Delaying further to reach the next full second.
  Setting Hardware Clock to 11:17:36 = 1469531856 seconds since 1969
  ioctl(RTC_SET_TIME) was successful.
  Not adjusting drift factor because it has been less than a day since the   last calibration.

In order to configure the Time Zone on red hat Linux machine ( version 5 and 6 ) need to configure the file:

/etc/sysconfig/clock

And create a symbolic link between

/etc/localtime to /usr/share/zoneinfo/America/New_York

but /etc/sysconfig/clock also required to set the ZONE variable as the following example:

ZONE="America/New_York"

So what is the need to set the variable ZONE=America/New_York when it is very clear from the link /etc/localtime that is pointed to /usr/share/zoneinfo/**America/New_York** ?

So what is the need to set the ZONE parameter with "America/New_York" value ?

Under /boot we have the following files ( red-hat Linux version 6.6 )

 cd /boot
 # ls -ltr

  drwx------ 2 root root    12288 Oct 15  2015 lost+found
 -rwxr-xr-x 1 root root  4152624 Oct 15  2015 vmlinuz-2.6.32-504.30.3.el6.x86_64
 -rw------- 1 root root  6084011 Oct 15  2015 initrd-2.6.32- 504.30.3.el6.x86_64kdump.img
  drwxr-xr-x 3 root root     1024 Oct 15  2015 efi
 -rw-r--r-- 1 root root   106371 Oct 15  2015 config-2.6.32-504.30.3.el6.x86_64
 -rw-r--r-- 1 root root  2546171 Oct 15  2015 System.map-2.6.32-504.30.3.el6.x86_64
 -rw-r--r-- 1 root root   200246 Oct 15  2015 symvers-2.6.32-504.30.3.el6.x86_64.gz
 -rw------- 1 root root 19360700 Oct 15  2015 initramfs-2.6.32-504.30.3.el6.x86_64.img
 -rwxr-xr-x 1 root root  4222736 Nov 23  2015 vmlinuz-2.6.32-573.12.1.el6.x86_64
 -rw-r--r-- 1 root root   107139 Nov 23  2015 config-2.6.32-573.12.1.el6.x86_64
 -rw-r--r-- 1 root root  2585672 Nov 23  2015 System.map-2.6.32-573.12.1.el6.x86_64
 -rw-r--r-- 1 root root   206008 Nov 23  2015 symvers-2.6.32-573.12.1.el6.x86_64.gz
 -rw------- 1 root root 24340354 Jul 16 03:20 initramfs-2.6.32-573.12.1.el6.x86_64.img
  drwxr-xr-x 2 root root     1024 Jul 16 03:20 grub

Because /boot size is very small, (90M size)

We want to delete the previous kernel from /boot include ALL the other files that related to this kernel

The current running kernel version

 # uname -r
 2.6.32-573.12.1.el6.x86_64

So now I want to capture all the files that are not related to the current kernel , and can be deleted from the /boot

egrep -v will do the Job

  # ls -ltr | egrep -v "2.6.32-573.12.1|lost\+found|grub|efi"

  -rwxr-xr-x 1 root root  4152624 Oct 15  2015 vmlinuz-2.6.32-504.30.3.el6.x86_64
  -rw------- 1 root root  6084011 Oct 15  2015 initrd-2.6.32-504.30.3.el6.x86_64kdump.img
  -rw-r--r-- 1 root root   106371 Oct 15  2015 config-2.6.32-504.30.3.el6.x86_64
  -rw-r--r-- 1 root root  2546171 Oct 15  2015 System.map-2.6.32-504.30.3.el6.x86_64
  -rw-r--r-- 1 root root   200246 Oct 15  2015 symvers-2.6.32-504.30.3.el6.x86_64.gz
  -rw------- 1 root root 19360700 Oct 15  2015 initramfs-2.6.32-504.30.3.el6.x86_64.img

  # rpm -qa | grep "2.6.32-504.30.3"
  kernel-2.6.32-504.30.3.el6.x86_64

so my plan is to perform the following

1. Remove the previos kernel

   rpm –e  kernel-2.6.32-504.30.3.el6.x86_64
   

2. Remove the following files from /boot

   rm config-2.6.32-504.30.3.el6.x86_64 
   rm System.map-2.6.32-504.30.3.el6.x86_64
   rm symvers-2.6.32-504.30.3.el6.x86_64.gz
   rm initramfs-2.6.32-504.30.3.el6.x86_64.img
   

My question:

Is my plan is risky ? , or I can be sure that my procedure is safe ?

How to force Linux to crash:

we installed the kexec-tools (kdump) on our redhat machines ( version 7.1 ) in order to capture problems by creating core file under /var/crash folder

we check that kdump is install as

 rpm -qa | grep kexec ( verify rpm kdump is installed )
 kexec-tools-2.0.7-19.el7_1.2.x86_64

we check the kdump service as

# /usr/bin/kdumpctl status 

Kdump is operational

we manually trigger the core dump using the following commands:

echo 1 > /proc/sys/kernel/sysrq
echo c > /proc/sysrq-trigger

The server should be reboot itself and the crash dump will be generated. Under /var/crash

bot nothing was happend

please advice way kdump not trigger the linux machine to reboot?

redhat doc about the KDUMP:

https://access.redhat.com/documentation/en-US/Red_Hat_Enterprise_Linux/7/pdf/Kernel_Crash_Dump_Guide/Red_Hat_Enterprise_Linux-7-Kernel_Crash_Dump_Guide-en-US.pdf

more /etc/redhat-release
Red Hat Enterprise Linux Server release 7.1 (Maipo)


  dmidecode |  grep -i VM
        Manufacturer: VMware, Inc.
        Product Name: VMware Virtual Platform

In Red Hat EL versions 5 and 6 we can easily to update the /etc/grub.conf in case we want to change the kernel by default variable

 For example , grub.conf on redhat 5
 default=0
 timeout=5
 #splashimage=(hd0,0)/grub/splash.xpm.gz
 #hiddenmenu
  title Red Hat Enterprise Linux Server (2.6.18-410.el5)
   root (hd0,0)
   kernel /vmlinuz-2.6.18-410.el5 ro root=/dev/rootvg/slash
   initrd /initrd-2.6.18-410.el5.img
  title Red Hat Enterprise Linux Server (2.6.18-409.el5)
    root (hd0,0)
   kernel /vmlinuz-2.6.18-409.el5 ro root=/dev/rootvg/slash
   initrd /initrd-2.6.18-409.el5.img

From this /etc/grub.conf if we want to boot from kernel 2.6.18-409 version then we just change the default=1. So on the next boot, the OS will start with the old kernel

RHEL7 is very different. I find in the RHEL7 the /boot/grub2/grub.cfg But I don't understand how to change the file in order to boot from other kernel as I do it on RHEL5.

We have in our organization around ~500 RedHat Linux machines.

On all the machines we installed applications and services under /etc/init.d, and oracle RAC servers. We intend to perform yum updates on all machines and after that take a reboot.

So I was wondering what command is safer:

reboot

or

shutdown -r now

is it possible to get the standard output from remote machine - 100 or 1 , After ruining the script /tmp/script.bash ?

 ssh $remote_machine /tmp/script.bash

 echo $? ( from remote machine script - not from ssh ! )

on remote machine -

 more /tmp/script.badsh

 #!/bin/bash

 command

 [[ $? -eq 0 ]] && exit 100 || exit 1

what are the diffrences between lvextend to lvresize as the below example?

 lvextend -L+1m /dev/mapper/rootvg-home
 lvresize -L+1m /dev/mapper/rootvg-home

dose the both examples do exactly the same ? ( increase +1M on /home )

second:

when I use the lvextend and try to increase the /home with 1M,

then lvextend round the size to 32M (increase /home by 32M ) ,

so is it possible to tell lvextend to grow only with 1M? by some additional flag?

 lvextend -L+1m /dev/mapper/rootvg-home
 Rounding size to boundary between physical extents: 32.00 MiB
 Size of logical volume rootvg/home changed from 320.00 MiB (10 extents) to  352.00 MiB (11 extents).
 Logical volume home successfully resized.

I just print the kernel rpms that need to install on my redhat machine (version 6.5)

# yum list-security --security | grep kernel-[0-9]

    RHSA-2014:1143 security kernel-2.6.18-371.12.1.el5.x86_64
    RHSA-2014:1959 security kernel-2.6.18-400.el5.x86_64
    RHSA-2014:2008 security kernel-2.6.18-400.1.1.el5.x86_64
    RHSA-2015:0164 security kernel-2.6.18-402.el5.x86_64
    RHSA-2015:0783 security kernel-2.6.18-404.el5.x86_64
    RHSA-2015:1042 security kernel-2.6.18-406.el5.x86_64
    RHSA-2016:0045 security kernel-2.6.18-408.el5.x86_64
    RHSA-2016:0450 security kernel-2.6.18-409.el5.x86_64

in case I want to install all security kernel rpms ( as displayed ) is that mean that all 8 (initrd & vmlinuz) kernels files will be installed under /boot ?

I am asking this question because I have small free available size on /boot

remark - the yum command that installed all the security packages is:

     yum -y update --security

example what I have now under /boot:

# ls /boot
   System.map-2.6.18-371.11.1.el5  grub                             lost+found                      vmlinuz-2.6.18-371.11.1.el5
   config-2.6.18-371.11.1.el5      initrd-2.6.18-371.11.1.el5.img  symvers-   2.6.18-371.11.1.el5.gz

installing of errata security kernel rpm ( from redhat sattelite ) on the linux red-hat,

could sometimes - create a diff 2-4 new update kernel under /boot ,

the problem here that /boot could be nearly %0 availbe space

is it possible to install only the latest rpm kernel and not all the previous kernels

I am not sure but I found the installonly_limit parameter from /etc/yum.conf

when we set installonly_limit=1 , does this mean to install always the latest kernel ?

for example

dose installonly_limit=1 ,

Tell us to keep to install only the higher rpm kernel release

and ignore installing the other old kernel version?

/etc/yum.conf 

installonly_limit=1

To list all available security updates without installing them, I run this

and this syntax is working on redhat 6 and 7

 # yum list-security --security

please advice what is the syntax for redhat 5?

I try the

 yum list-security --security

but this syntax not runing corectly on redhat 5

from redhat doc -

For Red Hat Enterprise Linux 5

To list all available security updates without installing them, run: Raw

     # yum list-security --security

we installed the following rpm's via yum on redhat version 5

# rpm -qa --last | head -10
  kernel-headers-2.6.18-408.el5                 Wed May 18 13:33:59 2016
  bind-utils-9.3.6-25.P1.el5_11.6               Wed May 18 13:33:59 2016
  redhat-release-5Server-5.11.0.2               Wed May 18 13:33:58 2016
  nss-3.19.1-4.el5_11                           Wed May 18 13:33:58 2016
  nspr-4.10.8-2.el5_11                          Wed May 18 13:33:58 2016
  bind-libs-9.3.6-25.P1.el5_11.6                Wed May 18 13:33:58 2016
  kernel-2.6.18-409.el5                         Wed May 18 04:13:58 2016

How can I tell if these RPMs were installed from scratch or just upgraded?

I try by rpm -qi

but from rpm -qi , we not get the info if rpm was installed from scratch or upgraded.

Secondly, if an rpm was upgraded then how can I downgrade it to the previous version?

example when I try to downgrade:

 yum downgrade openssh-server-5.3p1-117.el6.x86_64

 Loaded plugins: product-id, rhnplugin, security, subscription-manager
 This system is receiving updates from RHN Classic or RHN Satellite.
 Setting up Downgrade Process
 Only Upgrade available on package: openssh-server-5.3p1-117.el6.x86_64
 Nothing to do



  yum list 'openssh-server'

  Loaded plugins: product-id, rhnplugin, security, subscription-manager
  This system is receiving updates from RHN Classic or RHN Satellite.

  openssh-server.x86_64      5.3p1-117.el6
  Available Packages
  penssh-server.x86_64   5.3p1-118.1.el6_8 

we installed new server redhat version - 6.7 from kick start,

after installation complete successfully we get the login prompt

but I am unable to login locally on my redhat linux 6.7 server.

The login prompt keep getting again and again , and I cant get the passwd prompt

I restart the machine and access VIA single user mode ,

But can’t understand what are the files/conf that caused this issue or maybe something else?

please advise how to resolve this problem

from /var/log/secure

 17:35:47 linux_test login: permission denied 

We have installed Redhat Linux 6.5 from scratch the VIA kick start installation and booted into single user mode because I don't have the root password.

But when I perform the following:

passwd root
changing password for user root
passwd: permission denied 

Please advice what are the reasons that I get permission denied and how to resolve the problem.

We have couple of Linux servers all them are VM red hat Linux ( and they created by the Vsphere client , )

I want to know how we can capture on the Linux OS the following

1.Thick provision lazy zeroed

2.Thick provision eager zeroed

3.Thin provision

Is it possible to find files/conf on the linux redhat

And verify by this files the definition (1 or 2 or 3 ) ?

I have this in my linux machine

  grub>

how from this I start the linux machine as single user mode?

in order to update some file after boot

when I run the ethtool command on eth0 ( on VM machine redhat version 6.7 )

I see Supports auto-negotiation: No

can we change this to - auto-negotiation: yes ? , is it configurable?

 ethtool eth0
 Settings for eth0:
       Supported ports: [ TP ]
       Supported link modes:   1000baseT/Full
                            10000baseT/Full
       Supported pause frame use: No
       Supports auto-negotiation: No
       Advertised link modes:  Not reported
       Advertised pause frame use: No
       Advertised auto-negotiation: No
       Speed: 10000Mb/s
       Duplex: Full
       Port: Twisted Pair
       PHYAD: 0
       Transceiver: internal
       Auto-negotiation: off
       MDI-X: Unknown
       Supports Wake-on: uag
       Wake-on: d
       Link detected: yes

I have Linux machine red hat 7.2

because the dropping problem on eth1 interface

we perform the test according to red hat link - https://access.redhat.com/solutions/206223

finally we get the following results from crash tool

 crash> sym 0xffffffff8152aa5b
        ffffffff8152aa5b (t) __netif_receive_skb_core+1643 /usr/src/debug/kernel-3.10.0-327.10.1.el7/linux-3.10.0-327.10.1.el7.x86_64/net/core/dev.c: 3587
 crash> sym 0xffffffff8152aa5b
        ffffffff8152aa5b (t) __netif_receive_skb_core+1643 /usr/src/debug/kernel-3.10.0-327.10.1.el7/linux-3.10.0-327.10.1.el7.x86_64/net/core/dev.c: 3587
 crash> sym 0xffffffff81597290
        ffffffff81597290 (t) __udp4_lib_mcast_deliver+656 /usr/src/debug/kernel-3.10.0-327.10.1.el7/linux-3.10.0-327.10.1.el7.x86_64/net/ipv4/udp.c: 1683
 crash> sym 0xffffffff81560b58
        ffffffff81560b58 (t)  ip_error+104 /usr/src/debug/kernel-3.10.0-327.10.1.el7/linux-3.10.0-327.10.1.el7       .x86_64/net/ipv4/route.c: 938
  crash> sym 0xffffffff8151a448
         ffffffff8151a448 (T)  skb_queue_purge+24 /usr/src/debug/kernel-3.10.0-327.10.1.el7/linux-3.10.0-327.10         .1.el7.x86_64/net/core/skbuff.c: 2413
 crash> sym 0xffffffff815d3d7a
        ffffffff815d3d7a (t)    unix_stream_connect+714 /usr/src/debug/kernel-3.10.0-327.10.1.el7/linux-3.10.0-327.10.1.el7.x86_64/net/unix/af_unix.c: 1236
 crash> exit

please help me to understand the output from crash , what the meaning about the files path , dose this mean that problem is on the files ?

example from ifconfig about the dropping that increased every second:

   eth1: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 9000
         inet 12.1.2.10  netmask 255.255.252.0  broadcast 172.16.3.255
         ether 00:50:56:9f:11:de  txqueuelen 1000  (Ethernet)
         RX packets 196320  bytes 12640182 (12.0 MiB)
         RX errors 0  dropped 38071  overruns 0  frame 0  <--- drops