Linux tips and Howtos that I gathered over the years. Some of them might be old, so do your research. Some of them can be destructive, so be careful. Some of these saved me allot of time and disk space. Enjoy
Tar/ssh files example:
1
|
tar zcvf - /u01/ | ssh root@10.10.10.31 "cat > /OVS/backup/erpprd_apps_1450_16022011.tar.gz"
|
and to restore
1
2
|
cd /youlocation
ssh root@10.10.10.31 "cat /OVS/backup/erpprd_apps_1450_16022011.tar.gz" | tar zxvf -
|
Tar/ssh sparse files example:
Example 1:
1
|
tar -czSvf - 0004fb0000030000a5e8ff0ea5160ada/VirtualMachines/0004fb0000060000b3bd86f6aa8805cb/vm.cfg 0004fb0000030000a5e8ff0ea5160ada/VirtualDisks/eggy_osdisk.img 0004fb0000030000a5e8ff0ea5160ada/VirtualDisks/eggy_data_u01.img | ssh user@10.10.10.156 'cat - > /OVS/Repositories/0004fb00000300003e4055947747bd7f/eggy.tar.gz'
|
Example 2:
1
|
tar -czSvf - backup/ oracle/ | ssh root@eggy 'tar -C /mnt/disk/ -zSvxf -'
|
To create a sparse file on a Linux host
You can run dd with a count size of zero (this tells dd not to write any data to the file), and then use the seek option to extend the file to the desired size:
1
|
bash$ dd if=/dev/zero of=xen-guest.img bs=1 count=0 seek=8G
|
Once the sparse fie is created, you can use dd to verify how much space is allocated to it:
1
2
3
4
5
|
bash$ du -sh xen-guest.img
0 xen-guest.img
bash$ du -sh --apparent-size xen-guest.img
8.0G xen-guest.img
|
To create more loop devices on openSuse
vi /etc/modprobe.d/99-local.conf
1
|
options loop max_loop=20
|
Compressing apps and db files and splitting in 2G files
1
|
bash$ tar cvf - test|gzip|split -b2000m - /disk/test.tar.gz.split
|
Testing a tar.gz file
1
|
gunzip < dep_apps_all.tar.gz | tar tvf -
|
To rescan emulex bus for new luns
1
|
echo "- - -" > /sys/class/scsi_host/hostX/scan
|
Telegram troubleshooting
Command line string to send text to a user or group
1
|
curl 'https://api.telegram.org/botxxxxxxxxx:AAGApzqgDVY5x8lGyOMgUHzPEtjuqaCoY7s/sendMessage' -d chat_id='-xxxxxxxxx' -d text='This is a test messages'
|
routeing ip traffic to localhost
1
|
iptables -t nat -I OUTPUT --dst 5x.2x.2xx.1xx -p tcp --dport 3306 -j REDIRECT --to-ports 3306
|
check for process threads
1
2
3
4
5
6
7
8
9
10
|
ps -efL|grep -i prome| awk '{print $2}'|sort|uniq -c
6113 13751
1 15899
267 26295
211 31630
209 32402
200 54246
264 7594
ps -eLf | grep 13751 | wc
|
Restore broken LVM VG
Copy backup or archive file to root edit file and look for [missing]. Normally backup can be found at /etc/lvm/ Use below commands with care, it can brake your OS, if you don’t know what you are doing.
1
2
|
vgcfgrestore --list centos_os
vgcfgrestore -f /etc/lvm/archive/[backup_file] centos_os
|
Allowing user to use systemctl to manage services
Entry in your /etc/sudoers file:
1
2
3
|
User_Alias ADMINS_SYS = auser
Cmnd_Alias ADMINS_CMD = /bin/systemctl start httpd, /bin/systemctl stop httpd, /bin/systemctl reload httpd, /bin/systemctl restart httpd, /usr/bin/systemctl status httpd
ADMINS_SYS ALL = NOPASSWD: ADMINS_CMD
|
Always check your haproxy.cfg file
haproxy -c -V -f /etc/haproxy/haproxy.cfg
