LINUX AND VMWARE STUFF

Friday, October 5, 2018

Digging audit log with ausearch tool in RHEL 7

Kalaiselvan Nachimuthu Friday, October 05, 2018 0

ausearch is a tool to search audit daemon logs based upon the events based on different search criteria.

Audit system stores log entries in the /var/log/audit/audit.log file; if log rotation is enabled, rotated audit.log files are stored in the same directory.

Each event consists of three records, which share the same time stamp. Each record consists of several name=value pairs separated by a white space or a comma.

type=SYSCALL msg=audit(1510471123.129:36): arch=c000003e syscall=175 success=yes exit=0 a0=1901a20 a1=1c5d a2=41a2d8 a3=18fe400 items=0 ppid=7 24 pid=725 auid=4294967295 uid=0 gid=0 euid=0 suid=0 fsuid=0 egid=0 sgid=0 fsgid=0 tty=(none) ses=4294967295 comm="modprobe" exe="/usr/bin/kmo d" subj=system_u:system_r:insmod_t:s0 key=(null)
type=PROCTITLE msg=audit(1510471123.129:36): proctitle=2F7362696E2F6D6F6470726F6265002D71002D2D0069707461626C655F6D616E676C65
type=NETFILTER_CFG msg=audit(1510471123.276:37): table=nat family=2 entries=0

Here, ausearch utility allows us to search Audit log files for specific events. Also it is used to read the audit log timestamp to user readable timestamp by using -i (--interpret) option.

Example:

1.Search for hostname with given hostname specific.

[root@nsk ~]# ausearch -i -hn nsk.testingserver.internal
----
type=USER_AUTH msg=audit(10/04/2018 12:32:02.610:75) : pid=1617 uid=root auid=unset ses=unset subj=system_u:system_r:xdm_t:s0-s0:c0.c1023 msg='op=PAM:authentication grantors=pam_permit acct=gdm exe=/usr/libexec/gdm-session-worker hostname=nsk.testingserver.internal addr=? terminal=/dev/tty1 res=success'
----

2. Search only the first event that matches the search pattern.

[root@nsk ~]# ausearch -i -hn nsk.testingserver.internal --just-one
----
type=USER_AUTH msg=audit(10/04/2018 12:32:02.610:75) : pid=1617 uid=root auid=unset ses=unset subj=system_u:system_r:xdm_t:s0-s0:c0.c1023 msg='op=PAM:authentication grantors=pam_permit acct=gdm exe=/usr/libexec/gdm-session-worker hostname=nsk.testingserver.internal addr=? terminal=/dev/tty1 res=success'
[root@nsk ~]#

3. Search for all logged actions performed by user nsk, using the user's login ID (auid).

[root@nsk log]# ausearch -ua 1001 -i
----
type=LOGIN msg=audit(12/04/2017 11:39:18.052:156) : pid=1433 uid=root subj=system_u:system_r:sshd_t:s0-s0:c0.c1023 old-auid=unset auid=nsk tty=(none) old-ses=4294967295 ses=2 res=yes
----
type=USER_ROLE_CHANGE msg=audit(12/04/2017 11:39:18.991:157) : pid=1433 uid=root auid=nsk ses=2 subj=system_u:system_r:sshd_t:s0-s0:c0.c1023 msg='pam: default-context=unconfined_u:unconfined_r:unconfined_t:s0-s0:c0.c1023 selected-context=unconfined_u:unconfined_r:unconfined_t:s0-s0:c0.c1023 exe=/usr/sbin/sshd hostname=nsk addr=fe80::f24d:eb49:d219:6b0 terminal=ssh res=success'

4. Search for an event matching the given Process ID.

[root@nsk ~]# ausearch -i -p 2162
----
type=CRYPTO_SESSION msg=audit(10/05/2018 13:07:54.052:118) : pid=2162 uid=root auid=unset ses=unset subj=system_u:system_r:sshd_t:s0-s0:c0.c1023 msg='op=start direction=from-server cipher=aes256-ctr ksize=256 mac=hmac-sha2-256 pfs=curve25519-sha256@libssh.org spid=2163 suid=sshd rport=50935 laddr=10.0.2.15 lport=22 exe=/usr/sbin/sshd hostname=? addr=10.0.2.2 terminal=? res=success'
----

5. Search the /var/log/audit/audit.log file for successful login attempts

[root@nsk log]# ausearch --message USER_LOGIN --success yes --interpret
----
type=USER_LOGIN msg=audit(11/12/2017 13:04:08.279:110) : pid=662 uid=root auid=root ses=2 subj=system_u:system_r:local_login_t:s0-s0:c0.c1023
msg='op=login id=root exe=/usr/bin/login hostname=nsk addr=? terminal=tty1 res=success'
----
type=USER_LOGIN msg=audit(11/12/2017 13:05:46.297:107) : pid=1242 uid=root auid=root ses=1 subj=unconfined_u:unconfined_r:unconfined_t:s0-s0:c
0.c1023 msg='op=login id=root exe=/usr/sbin/sshd hostname=10.0.2.2 addr=10.0.2.2 terminal=/dev/pts/0 res=success'
----

6. Search for all account and group activities.

[root@nsk log]# ausearch -m ADD_USER -m DEL_USER -m ADD_GROUP -m DEL_GROUP -i
----
type=ADD_GROUP msg=audit(11/15/2017 22:05:29.396:169) : pid=15764 uid=root auid=root ses=2 subj=unconfined_u:unconfined_r:groupadd_t:s0-s0:c0.c1023 msg='op=add-group id=dovecot exe=/usr/sbin/groupadd hostname=? addr=? terminal=? res=success'
----
type=ADD_USER msg=audit(11/15/2017 22:05:29.431:171) : pid=15769 uid=root auid=root ses=2 subj=unconfined_u:unconfined_r:useradd_t:s0-s0:c0.c1023 msg='op=add-user id=dovecot exe=/usr/sbin/useradd hostname=? addr=? terminal=? res=success'

7. Search for all failed PROCTITLE from yesterday up until now

[root@nsk log]# ausearch --start yesterday --end now -m PROCTITLE -sv no -i
----
type=PROCTITLE msg=audit(10/03/2018 18:00:02.623:71) : proctitle=/usr/sbin/httpd -DFOREGROUND
type=SYSCALL msg=audit(10/03/2018 18:00:02.623:71) : arch=x86_64 syscall=open success=no exit=EACCES(Permission denied) a0=0x560fb5acc008 a1=O_RDONLY a2=0x1b6 a3=0x24 items=0 ppid=1 pid=1145 auid=unset uid=root gid=root euid=root suid=root fsuid=root egid=root sgid=root fsgid=root tty=(none) ses=unset comm=httpd exe=/usr/sbin/httpd subj=system_u:system_r:httpd_t:s0 key=(null)
type=AVC msg=audit(10/03/2018 18:00:02.623:71) : avc: denied { read } for pid=1145 comm=httpd name=php-mapi.cfg dev="dm-0" ino=19498435 scontext=system_u:system_r:httpd_t:s0 tcontext=system_u:object_r:zarafa_etc_t:s0 tclass=file

Please refer man ausearch for more option.

Tags # Linux General Continue Reading

Thursday, October 4, 2018

How to read/convert Audit log timestamp in RHEL7

Kalaiselvan Nachimuthu Thursday, October 04, 2018 0

By default, audit log would be like below.

type=SYSCALL msg=audit(1510471123.129:36): arch=c000003e syscall=175 success=yes exit=0 a0=1901a20 a1=1c5d a2=41a2d8 a3=18fe400 items=0 ppid=7 24 pid=725 auid=4294967295 uid=0 gid=0 euid=0 suid=0 fsuid=0 egid=0 sgid=0 fsgid=0 tty=(none) ses=4294967295 comm="modprobe" exe="/usr/bin/kmo d" subj=system_u:system_r:insmod_t:s0 key=(null)
type=PROCTITLE msg=audit(1510471123.129:36): proctitle=2F7362696E2F6D6F6470726F6265002D71002D2D0069707461626C655F6D616E676C65 type=NETFILTER_CFG msg=audit(1510471123.276:37): table=nat family=2 entries=0

Below commands are used to convert the auditlog timestamp to user readable timestamp.

1. AUSEARCH :

ausearch utility allows us to search Audit log files for specific events. Also it is used to read the audit log epoch timestamp to user readable timestamp.By default, ausearch searches the /var/log/audit/audit.log file. We can specify a different file using the ausearch options -if file_name command

[root@nsk log]# ausearch -i | grep -i CONFIG
type=CONFIG_CHANGE msg=audit(11/12/2017 12:48:40.357:5) : audit_backlog_limit=8192 old=64 auid=unset ses=unset subj=system_u:system_r:unconfined_service_t:s0 res=yes
type=CONFIG_CHANGE msg=audit(11/12/2017 12:48:40.357:6) : audit_failure=1 old=1 auid=unset ses=unset subj=system_u:system_r:unconfined_service_t:s0 res=yes

-i, --interpret : Interpret numeric entities into text

2. DATE :

A) Date command with %s is used to convert normal time to epoch time.
%s : seconds since 1970-01-01 00:00:00 UTC

Display the current time in the given FORMAT, or set the system date
[root@nsk audit]# date +%s
1538570770
[root@nsk audit]# date +%s
1538570773

B) Date command with -d@ is used to convert epoch time to normal time.
[root@nsk audit]# date -d@1538570776
Wed Oct 3 18:16:16 IST 2018
[root@nsk audit]#

C) If we want to convert the specific system time to epoch time.
[root@nsk audit]# date --date="Wed Oct 3 18:16:16 IST 2018" +%s
1538570776

3. PERL : Perl was originally a language optimized for scanning arbitrary text files, extracting information from those text files, and printing reports based on that information

[root@nsk audit]# perl -pe 's/(\d+)/localtime/e' audit.log | more
type=DAEMON_START msg=audit(Sun Nov Wed Oct 3 20:22:26 2018 12:48:40 2017.186:6974): op=start ver=2.7.6 format=raw kernel=3.10.0-693.el7.x86_64 auid=4294967295 pid=606 uid=0 ses=4294967295 subj=system_u:system_r:auditd_t:s0 res=success
type=CONFIG_CHANGE msg=audit(Sun Nov Wed Oct 3 20:22:26 2018 12:48:40 2017.357:5): audit_backlog_limit=8192 old=64 auid=4294967295 ses=429496 7295 subj=system_u:system_r:unconfined_service_t:s0 res=1

Here,
-p : Print out the pattern space
-e : command (This command allows one to pipe input from a shell command into pattern space)
localtime : it is perl function, it is having 9 elements.
-d : Match 1 or more repetition of digits

Tags # Linux General Continue Reading

Wednesday, October 3, 2018

How to rebuild the GRUB configuration file in RHEL7

Kalaiselvan Nachimuthu Wednesday, October 03, 2018 0

Rebuilding the GRUB configuration file in RHEL7

Situation : Whenever there is inconsistency in the GRUB file, empty grub configuration or of the grub file got removed accidentally, follow the below steps to fix the grub issue.

Solution:

STEP 1 : List the partitions by using “ ls “ command
grub > ls
(proc) (hd0) (hd0,msdos3) (hd0,msdos2) (hd0,msdos1) (fd0)

STEP 2: Findout the root partitions by using command ls < partition name >. Run ls command to all above listed available partitions.

STEP 3: Set the root partition. In our case its present in (hd0,msdos1)

grub> set root=(hd0,msdos1)

grub>

STEP 4: Type Linux and specify the kernel or Press tab for listing the available kernel. Once choosing it, we have to specify the root volume (In our example its /dev/sda1).

grub> linux /vmlinuz-3.10.0-229.el7.x86_64 ro root=/dev/sda1

STEP 5: Specify the initramfs image press tab for listing it. Choose the initramfs image with the same kernel version.

grub> initrd /initramfs-3.10.0-229.el7.x86_64.img

Execute 'boot' command to boot the server with above configuration.

Once the server is up, use grub2-mkconfig command to rebuild the grub.conf file.

[root@nsk /]grub2-mkconfig -o /boot/grub2/grub.cfg

Generating grub configuration file ...

Found linux image: /boot/vmlinuz-3.10.0-229.el7.x86_64

Found initrd image: /boot/initramfs-3.10.0-229.el7.x86_64.img

...

done

Finally verify the grub file under /boot/grub2/

[root@nsk /]# cd /boot/grub2/

[root@nsk grub2]# ls

device.map fonts grub.cfg grubenv i386-pc locale

Reboot the server and verify one more time.

Tags # Linux Troubleshooting Continue Reading

Friday, September 14, 2018

python: SELinux is preventing httpd from connectto access on the unix_stream_socket /var/lib/mysql/mysql.sock - Mariadb running on RHEL 7

Kalaiselvan Nachimuthu Friday, September 14, 2018 0

SELinux is preventing the httpd access by default.

Situation
While connecting mysql database from web, getting this error.
python: SELinux is preventing httpd from connectto access on the unix_stream_socket /var/lib/mysql/mysql.sock

Solution
Run below command to allow httpd in Selinux.

[root@nsk ~]# ausearch -c 'httpd' --raw | audit2allow -M my-httpd
******************** IMPORTANT ***********************
To make this policy package active, execute:

semodule -i my-httpd.pp

[root@nsk ~]# semodule -i my-httpd.pp

Hope it helps.

Tags # Linux General Continue Reading

Friday, September 7, 2018

ERROR 2002 (HY000): Can't connect to local MySQL server through socket '/var/lib/mysql/mysql.sock' - Mariadb running on RHEL7

Kalaiselvan Nachimuthu Friday, September 07, 2018 0

Situation :
I have tried to login as root to MariaDB Database in Linux Server, Getting below error.

[root@nsk ~]# mysql -u root -p
Enter password:
ERROR 2002 (HY000): Can't connect to local MySQL server through socket '/var/lib/mysql/mysql.sock'

Solution:
We need to recover the root password of mariadb. Follow the below steps to achieve root password recovery.

STEP 1 : Stop the mariadb service
[root@nsk ~]# systemctl stop mariadb.service
[root@nsk ~]#

STEP 2 : Run mysql in safe mode
[root@nsk ~]# mysqld_safe --skip-grant-tables &
[1] 8051
[root@nsk ~]# 180907 13:23:49 mysqld_safe Logging to '/var/log/mariadb/mariadb.log'.
180907 13:23:49 mysqld_safe Starting mysqld daemon with databases from /var/lib/mysql

STEP 3 : Login as root and select mysql db. Then reset root password.
[root@nsk ~]# mysql -u root -p
Enter password:
Welcome to the MariaDB monitor. Commands end with ; or \g.
Your MariaDB connection id is 1
Server version: 5.5.60-MariaDB MariaDB Server

Copyright (c) 2000, 2018, Oracle, MariaDB Corporation Ab and others.

Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.

MariaDB [(none)]> show databases;
+-------------------------------+
| Database |
+-------------------------------+
| information_schema |
| company |
| mydb |
| mysql |
| performance_schema |
| test |
+-------------------------------+
6 rows in set (0.00 sec)

MariaDB [(none)]> use mysql;
Database changed
MariaDB [mysql]> update user set password=PASSWORD("NewPassword") where User='root';
Query OK, 0 rows affected (0.00 sec)
Rows matched: 3 Changed: 0 Warnings: 0

MariaDB [mysql]>
MariaDB [mysql]> flush privileges;
Query OK, 0 rows affected (0.00 sec)

MariaDB [mysql]> quit
Bye

STEP 4 : Now stop and start the mariadb service and test the new password.

[root@nsk ~]# systemctl stop mariadb.service
[root@nsk ~]#
[root@nsk ~]# systemctl start mariadb.service
[root@nsk ~]#
[root@nsk ~]# mysql -u root -p
Enter password:
Welcome to the MariaDB monitor. Commands end with ; or \g.
Your MariaDB connection id is 5
Server version: 5.5.60-MariaDB MariaDB Server

Copyright (c) 2000, 2018, Oracle, MariaDB Corporation Ab and others.

Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.

MariaDB [(none)]>

Hope it helps.

Tags # General Topic Continue Reading

Tuesday, September 4, 2018

Error: Cannot retrieve metalink for repository: epel. Please verify its path and try again - SOLVED

Kalaiselvan Nachimuthu Tuesday, September 04, 2018 0

Situation : I have installed epel-release-latest-6.noarch.rpm on CentOS release 6.10 (Final) and trying to install
python-pip, but getting the below error.

[root@puppetlabs tmp]# rpm -ivh epel-release-latest-6.noarch.rpm
warning: epel-release-latest-6.noarch.rpm: Header V3 RSA/SHA256 Signature, key ID 0608b895: NOKEY
Preparing... ########################################### [100%]
1:epel-release ########################################### [100%]
[root@puppetlabs tmp]#
[root@puppetlabs tmp]# yum install python-pip
Loaded plugins: fastestmirror
Setting up Install Process
Loading mirror speeds from cached hostfile
Error: Cannot retrieve metalink for repository: epel. Please verify its path and try again

Solution:

Edit both /etc/yum.repos.d/epel.repo and /etc/yum.repos.d/epel-testing.repo files, commenting all entries
starting with mirrorlist= and uncomment all the entries starting with baseurl=

epel.repo base url is changed from http://download.fedoraproject.org/pub/epel/6/ to http://del-repos.extreme-ix.org/epel/6/x86_64/repodata/ update the same.
epel-testing.repo base url is changed from http://del-repos.extreme-ix.org/epel/testing/6/ to http://del-repos.extreme-ix.org/epel/testing/6 update the same.

Now run yum repolist command.

[root@puppetlabs yum.repos.d]# yum repolist
Loaded plugins: fastestmirror
Loading mirror speeds from cached hostfile
* base: centos.mirror.far.fi
* extras: centos.mirror.far.fi
* updates: centos.mirror.far.fi
repo id repo name status
base CentOS-6 - Base 6,713
epel Extra Packages for Enterprise Linux 6 - x86_64 12,522
extras CentOS-6 - Extras 31
updates CentOS-6 - Updates 114
repolist: 19,380

Hope it helps.

Tags # Linux General Continue Reading

Monday, September 3, 2018

How to reduce (lvreduce) the Logical Volume in Linux Server

Kalaiselvan Nachimuthu Monday, September 03, 2018 0

How to reduce (lvreduce) the Logical Volume in Linux Server.

Situation

Here, /app1 is 100GB filesystem. We need to reduce it to 70GB

[root@testserver ~]# df -hP
Filesystem Size Used Avail Use% Mounted on
/dev/mapper/vg_main-lv_root 31G 2.0G 28G 7% /
tmpfs 3.7G 0 3.7G 0% /dev/shm
/dev/xvdb1 477M 93M 355M 21% /boot
/dev/mapper/vg_DPFERT-lv_app1 99G 11G 84G 11% /app1

[root@testserver ~]# vgs
VG #PV #LV #SN Attr VSize VFree
vg_DPFERT 1 1 0 wz--n- 100.00g 0
vg_main 1 2 0 wz--n- 31.50g 0

[root@testserver ~]# fdisk -l /dev/xvdc

Disk /dev/xvdc: 107.4 GB, 107374182400 bytes
255 heads, 63 sectors/track, 13054 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x00000000

Device Boot Start End Blocks Id System
/dev/xvdc1 1 13054 104856254+ 8e Linux LVM

STEP 1 : First Unmount the LV

STEP 2 : Run e2fsck command to check the file system

[root@testserver ~]# e2fsck -f /dev/vg_DPFERT/lv_app1
e2fsck 1.43-WIP (20-Jun-2013)
Pass 1: Checking inodes, blocks, and sizes
Pass 2: Checking directory structure
Pass 3: Checking directory connectivity
Pass 4: Checking reference counts
Pass 5: Checking group summary information
/dev/vg_DPFERT/lv_app1: 57971/6553600 files (0.2% non-contiguous), 3073907/26213376 blocks

STEP 3 : Run resize2fs command for resizing the file system.

[root@testserver ~]# resize2fs /dev/vg_DPFERT/lv_app1 70G
resize2fs 1.43-WIP (20-Jun-2013)
Resizing the filesystem on /dev/vg_DPFERT/lv_app1 to 18350080 (4k) blocks.
The filesystem on /dev/vg_DPFERT/lv_app1 is now 18350080 blocks long.

STEP 4 : Run lvreduce command to resuce the lvsize.

[root@testserver ~]# lvreduce -L 70G /dev/vg_DPFERT/lv_app1
WARNING: Reducing active logical volume to 70.00 GiB
THIS MAY DESTROY YOUR DATA (filesystem etc.)
Do you really want to reduce lv_app1? [y/n]: y
Size of logical volume vg_DPFERT/lv_app1 changed from 100.00 GiB (25599 extents) to 70.00 GiB (17920 extents).
Logical volume lv_app1 successfully resized
[root@testserver ~]#

STEP 5 : Mount the LV
[root@testserver ~]# lvs
LV VG Attr LSize Pool Origin Data% Meta% Move Log Cpy%Sync Convert
lv_app1 vg_DPFERT -wi-a----- 70.00g
lv_root vg_main -wi-ao---- 31.22g
lv_swap vg_main -wi-ao---- 288.00m

[root@testserver ~]# vgs
VG #PV #LV #SN Attr VSize VFree
vg_DPFERT 1 1 0 wz--n- 100.00g 30.00g
vg_main 1 2 0 wz--n- 31.50g 0

[root@testserver home]# df -hP
Filesystem Size Used Avail Use% Mounted on
/dev/mapper/vg_main-lv_root 31G 2.0G 28G 7% /
tmpfs 3.7G 0 3.7G 0% /dev/shm
/dev/xvdb1 477M 93M 355M 21% /boot
/dev/mapper/vg_DPFERT-lv_app1 69G 11G 56G 16% /app1

Hope it helps.

Tags # LVM Continue Reading

LINUX AND VMWARE STUFF

Friday, October 5, 2018

Digging audit log with ausearch tool in RHEL 7

Thursday, October 4, 2018

How to read/convert Audit log timestamp in RHEL7

Wednesday, October 3, 2018

How to rebuild the GRUB configuration file in RHEL7

Friday, September 14, 2018

python: SELinux is preventing httpd from connectto access on the unix_stream_socket /var/lib/mysql/mysql.sock - Mariadb running on RHEL 7

Friday, September 7, 2018

ERROR 2002 (HY000): Can't connect to local MySQL server through socket '/var/lib/mysql/mysql.sock' - Mariadb running on RHEL7

Tuesday, September 4, 2018

Error: Cannot retrieve metalink for repository: epel. Please verify its path and try again - SOLVED

Monday, September 3, 2018

How to reduce (lvreduce) the Logical Volume in Linux Server

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